City of God XX.29:

Chapter 29.-Of the Coming of Elias Before the Judgment, that the Jews May Be Converted to Christ by His Preaching and Explanation of Scripture.

After admonishing them to give heed to the law of Moses, as he foresaw that for a long time to come they would not understand it spiritually and rightly, he went on to say, "And, behold, I will send to you Elias the Tishbite before the great and signal day of the Lord come: and he shall turn the heart of the father to the son, and the heart of a man to his next of kin, lest I come and utterly smite the earth." It is a familiar theme in the conversation and heart of the faithful, that in the last days before the judgment the Jews shall believe in the true Christ, that is, our Christ, by means of this great and admirable prophet Elias who shall expound the law to them. For not without reason do we hope that before the coming of our Judge and Saviour Elias shall come, because we have good reason to believe that he is now alive; for, as Scripture most distinctly informs us, he was taken up from this life in a chariot of fire. When, therefore, he is come, he shall give a spiritual explanation of the law which the Jews at present understand carnally, and shall thus "turn the heart of the father to the son," that is, the heart of fathers to their children; for the Septuagint translators have frequently put the singular for the plural number. And the meaning is, that the sons, that is, the Jews, shall understand the law as the fathers, that is, the prophets, and among them Moses himself, understood it. For the heart of the fathers shall be turned to their children when the children understand the law as their fathers did; and the heart of the children shall be turned to their fathers when they have the same sentiments as the fathers. The Septuagint used the expression, "and the heart of a man to his next of kin," because fathers and children are eminently neighbors to one another. Another and a preferable sense can be found in the words of the Septuagint translators, who have translated Scripture with an eye to prophecy, the sense, viz., that Elias shall turn the heart of God the Father to the Son, not certainly as if he should bring about this love of the Father for the Son, but meaning that he should make it known, and that the Jews also, who had previously hated, should then love the Son who is our Christ. For so far as regards the Jews, God has His heart turned away from our Christ, this being their conception about God and Christ. But in their case the heart of God shall be turned to the Son when they themselves shall turn in heart, and learn the love of the Father towards the Son.

On the Psalms (Ps. LXXIV, para 10) (NPNF, Vol 8, pages 345-346) cites the account of Moses' hand turning white with leprosy and then being restored to health as a prefigurement of the restoration of Israel after its initial rejection of Christ.

On the Psalms (Ps. LXXXIX, para 35) (NPNF, Vol 8,pages 438-439): "After these stern penalties which have been recorded as having been inflicted upon this people and kingdom (Israel), that God might not be supposed to have fulfilled His promises in it, and so not to grant another kingdom in Christ, of which kingdom there shall be no end, the prophet addresses Him in these words, 'Lord, how long wilt Thou hid Thyself unto the end?' (v 46). For possibly it was not from them and to the end; because 'blindness in part is happened to Israel, until the fulness of the Genitles be come in, and so all Israel shall be saved.' but in the mean while 'shall Thy wrath burn like fire.'"

"Their sins occasioned the salvation of the Gentiles and again the incredulity of the Gentiles will occasion the conversion of Israel. You will find both in the Apostle (St. Paul)."

Homilies on the Gospel of Matthew HOMILY LVII:

For the Scriptures speak of two advents of Christ, both this that is past, and that which is to come; and declaring these Paul said, "The grace of God, that bringeth salvation, hath appeared, teaching us, that, denying ungodliness and worldly lusts, we should live soberly, and righteously, and godly."Behold the one, hear how he declares the other also; for having said these things, he added, "Looking for the blessed hope and appearing of our great God and Saviour Jesus Christ."And the prophets too mention both; of the one, however, that is, of the second, they say Elias will be the forerunner. For of the first, John was forerunner; whom Christ called also Elias, not because he was Elias, but because he was fulfilling the ministry of that prophet. For as the one shall be forerunner of the second advent, so was the other too of the first. But the Scribes, confusing these things and perverting the people, made mention of that other only to the people, the second advent, and said, "If this man is the Christ, Elias ought to have come beforehand." Therefore the disciples too speak as follows, "How then say the Scribes, Elias must first come ?" Therefore also the Pharisees sent unto John, and asked him, "Art thou Elias?"making no mention anywhere of the former advent. What then is the solution, which Christ alleged? "Elias indeed cometh then, before my second advent; and now too is Elias come;" so calling John. In this sense Elias is come: but if thou wouldest seek the Tishbite, he is coming. Wherefore also He said, "Elias truly cometh, and shall restore all things."All what things? Such as the Prophet Malachi spake of; for "I will send you," saith He, "Elias the Tishbite, who shall restore the heart of father to son, lest I come and utterly smite the earth." Seest thou the accuracy of prophetical language? how, because Christ called John, Elias, by reasoning of their community of office, lest thou shouldest suppose this to be the meaning of the prophet too in this place, He added His country also, saying, "the Tishbite;"whereas John was not a Tishbite. And herewith He sets down another sign also, saying, "Lest I come and utterly smite the earth," signifying His second and dreadful advent. For in the first He came not to smite the earth. For, "I came not," saith He, "to judge the world, but to save the world." To show therefore that the Tishbite comes before that other advent, which hath the judgment, He said this. And the reason too of his coming He teaches withal. And what is this reason? That when He is come, he may persuade the Jews to believe in Christ, and that they may not all utterly perish at His coming. Wherefore He too, guiding them on to that remembrance, saith, "And he shall restore all things;" that is, shall correct the unbelief of the Jews that are then in being. Hence the extreme accuracy of his expression; in that he said not, "He will restore the heart of the son to the father," but "of the father to the son."For the Jews being fathers of the apostles, his meaning is, that he will restore to the doctrines of their sons, that is, of the apostles, the hearts of the fathers, that is, the Jewish people's mind. "But I say unto you, that Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of Man suffer of them. Then they understood that He spake to them of John." And yet neither the Scribes said this, nor the Scriptures; but because now they were sharper and more attentive to His sayings, they quickly caught His meaning. And whence did the disciples know this? He had already told them, "He is Elias, which was for to come;"but here, that he hath come; and again, that "Elias cometh and will restore all things." But be not thou troubled, nor imagine that His statement wavers, though at one time He said, "he will come," at another, "he hath come." For all these things are true. Since when He saith, "Elias indeed cometh, and will restore all things," He means Elias himself, and the conversion of the Jews which is then to take place; but when He saith, "Which was for to come," He calls John, Elias, with regard to the manner of his administration. Yea, and so the prophets used to call every one of their approved kings, David; and the Jews, "rulers of Sodom,"and "sons of Ethiopians;" because of their ways. For as the other shall be forerunner of the second advent, so was this of the first.

Homily XIX on Rom. 11, Ver 12 (NPNF Vol 11, page 489):

 "Now if the fall of them be the riches of the world, and diminishing of them the riches of the Gentiles, how much more their fulness?...' For if when they stumbled, he says, so many enjoyed salvation, and when they were case out so many were called, just consider what will be the case when they return. ....Now, he does not say, 'how much more their'return, or their altering, or their well-doing, but 'how much more their fulness', that is, when they are all about coming in."

Homily XIX on Rom. 11, Ver 15 (NPNF Vol 11, page 490):

"'For if the casting away of them be the reconciling of the world, what shall the receiving of them be but life from the dead?' ....But see also even in his favors to them, how he solaces them in words only. 'For if the casting away of them be the reconciling of the world,' (and what is this to the Jews?) 'what shall the receiving of them be but life from the dead?' Yet even this was no boon to them, unless they had been received. But what he means is to this effect: If in anger with them He gave other men so great gifts, when He is reconciled to them what will He not give?'"

Homily XIX on Rom. 11 ver. 27:
“For this is my covenant unto them, when I shall take away their sins”.  Not when they are circumcised….but when theey attain to the forgiveness of sins.  If then this hath been promised, but has never yet happened in their case, nor have they ever enoyed the remission of sins by baptism, certainly it will come to pass.

De Fide Orthodoxa (IV, 26, "Concerning the Antichrist"):

It should be known that the Antichrist is bound to come. Every one, therefore, who confesses not that the Son of God came in the flesh and is perfect God and became perfect man, after being God, is Antichrist. But in a peculiar and special sense he who comes at the consummation of the age is called Antichrist. First, then, it is requisite that the Gospel should be preached among all nations, as the Lord said, and then he will come to refute the impious Jews…
But Enoch and Elias the Thesbite shall be sent and shall turn the hearts of the fathers to the children, that is, the synagogue to our Lord Jesus Christ and the preaching of the apostles: and they will be destroyed by him. And the Lord shall come out of heaven, just as the holy apostles beheld Him going into heaven, perfect God and perfect man, with glory and power, and will destroy the man of lawlessness, the son of destruction, with the breath of His mouth. Let no one, therefore, look for the Lord to come from earth, but out of Heaven, as He himself has made sure.

Moralia in Iob (Preface, X, 20):

 "After the loss of Job's possessions, after all his bereavements, after all the suffering of his wounds, after all his angry debates, it is good that he is consoled by twofold repayment. In just this way does the holy church, while it is still in this world, receive twofold reward for the trials it sustains, when all the gentile nations have been brought into its midst, at the end of time, and the church converts even the hearts of the Jews to its cause.  Thus it is written, 'Until the fulness of nations enters and so all Israel is saved.'"

Homilia 22 in Evangelia:
Dearly beloved brethren, the portion of the Holy Gospel which hath just now been read in your ears, is exceeding simple on the face of it, which is its historical sense ; but the mystic sense, which underlieth that other, requireth from us a little searching.  Mary Magdalene came unto the Sepulchre when it was yet dark.  The historic sense telleth us what was the hour of the day ; the mystic sense, the state of her understanding who sought.  Mary Magdalene sought for him, by whom all things were made, and whom she had seen die, as concerning the flesh ; she sought for him, I say, in the grave, and finding him not, she believed that he had been stolen away.  Yea, it was yet dark, when she came unto the sepulchre.  Then she ran and told the disciples, but they who had loved him most, namely Peter and John, did outrun the others.
So they ran both together, but John did outrun Peter, and came first to the Sepulchre, but yet took he not upon himself to go in first.  Then cometh Peter following him, and went in.  What, my brethren, what did the racing of these Apostles signify?  Can we believe that the description given by the deepest of the Evangelists is without a mystic interpretation?  By no means.  John had never told how that he did outrun Peter, and yet went not into the Sepulchre, if he had not believed that his hesitation veiled some mystery.  What signifieth John but the Synagogue? or Peter, but the Church?
Neither must ye take it as strange that the elder Apostle should represent the Church, and younger the Synagogue : for although the Synagogue was first to worship God, yet the herd of Gentiles is in the world older than the Synagogue, as witnesseth Paul where he saith : That was not first which is spiritual, but that which is natural.  By Peter, then, who was the elder, is signified the Church of the Gentiles ; and by John, who was the younger, the Synagogue of the Jews.  They run both of them together, for from the time of her birth until now (and so will it be until the end), the Church of the Gentiles hath run in a parallel road and manywise a common road with the Synagogue, albeit not with equal understandings.  The Synagogue came first to the Sepulchre, but she hath not yet entered in ; for, though she hath received the commandments of the law, and hath heard the Prophets tell of the Incarnation and Passion of the Lord, she will not believe in him who died for her.

"Paul insists that only a part of Israel has been hardened, for many of them believe.  He thus encourages them not to despair that others will be saved as well.  After the Gentiles accepted the gospel, the Jews would believe, when the great Elijah would come to them and bring them the doctrine of the faith.  The Lord himself said as much: 'Elijah will come and will restore all things.'"

in his Explanation of the Apocalypse, "it is well believed that the wicked Jews will be deceived as well as deceive, but that others will understand the law spiritually through the instruction of the great prophet Elijah, and will be incorporated among the members of the Church, and bravely overcome the enemy." 

In a letter to his Abbot Eusebius about his Explanatio:"He has foretold that the Jews are to be made subject to the Church, and that there is to be a trial of the world at large, and that He Himself will come quickly."

"Lest the Antichrist come suddenly and without warning and deceive and destroy the whole human race by his error, before his arrival the two great prophets Enoch and Elijah will be sent into the world. They will defend God's faithful against the attack of the Antichrist with divine arms and will instruct, comfort, and prepare the elect for battle with three and a half years teaching and preaching. These two very great prophets and teachers will convert the sons of Israel who will live in that time to the faith, and they will make their belief unconquerable among the elect in the face of the affliction of so great a storm. At that time what scripture says will be fulfilled 'If the number of sons of Israel be like the sand of the sea, their remnant will be saved'."

"The blindness of the Jews will endure until the fullness of the gentiles have accepted the faith.  And this is in accord with what the Apostle says below about the salvation of the Jews, namely, that after the fullness of the nations have entered, 'all Israel will be saved', not individually as at present, but universally." ...

 "What, I say, will such an admission effectuate, if not that it bring the Gentiles back to life? The Gentiles would be the believers whose faith has grown cold, or even that the totality, deceived by the Antichrist, fall and are restored to their pristine fervor by the admission of the Jews."

 "the coming of Enoch and Elias, who live even now and shall live until they come to oppose Antichrist himself, and to preserve the elect in the faith of Christ, and in the end shall convert the Jews, and it is certain that this is not yet fulfilled."

“not displeasing to the Lord, but rather, acceptable to Him that the Dispersion of the Jews should live and do service under Catholic Kings and Christian princes – the remnants of which then will finally be saved (Romans 9:3-24), since in those days Judah will be saved (Jeremiah 33:6-26) and Israel will dwell in mutual trust.”

“Whereas the Jews are made to the image of God, and a remnant of them will one day be saved, and whereas they have sought our protection: following in the footsteps of our predecessors We command that they be not molested in their synagogues; that their laws, rights and customs be not assailed; that they be not baptized by force, constrained to observe Christian festivals, nor to wear new badges, and that they be not hindered in their business relations with Christians.”

 in his commentary on Matthew 17:11-12 ("Elijah does come, and he is to restore all things; but I tell you that Elijah has already come, and they did not know him, but did to him whatever they pleased. So also the Son of man will suffer at their hands.") states that Elias will: "Restore all things: that is, convert the Jews to Christ as the Messiah promised to themselves and there forefathers." 

on Matthew 23:37-39 ("O Jerusalem, Jerusalem, killing the prophets and stoning those who are sent to you! How often would I have gathered your children together as a hen gathers her brood under her wings, and you would not!  Behold, your house is forsaken and desolate. For I tell you, you will not see me again, until you say, 'Blessed is he who comes in the name of the Lord.'"): "It is possible that this passage may be understood of the Jews, who about the end of the world shall be converted to Christ by the preaching of Elias, and who, when He shall presently come to judgment, will acknowledge Him to be the Messiah, the Blessed of the Lord."

(B) Universal and Cosmic Eschatology.- 6) Notwhithstanding Christ's express refusal to specify the time of the end (Mrak xiii, 32, Acts i, 6 sq) it was a common belief among early Christians that the end of the world was near. This seemed to have some support in certain sayings of Christ in reference to the destruction of Jerusalem, which are set down in the Gospels side by side with the prophecies relating to the end (Matt 24, Luke 21), and in certain passages of the Apostolic writings, which might, not unnaturally, have been so understood (but see II Thes, ii, s2 sqq) where St. Paul corrects this impression.) On the other hand, Christ had clearly stated that the Gospel was to be preached to all the nations before the end (Matt 24:14) and St. Paul looked forward to the ultimate conversion of the Jewish people as a remote event to be preceded by the conversion of the Gentiles (Rom xi, 25 sqq).

"Conversion of the Jews: According to the interpretation of the Fathers, the conversion of the Jews towards the end of the world is foretold by St. Paul in the Epistle to the Romans (11:25-26): 'For I would not have you ignorant, brethren, of this mystery, . . . that blindness in part has happened in Israel, until the fullness of the Gentiles should come in. And so all Israel should be saved as it is written: There shall come out of Sion, he that shall deliver, and shall turn away ungodliness from Jacob.'"

"From the present, (verses) 1-24, St. Paul turns his attention to the future.  The time will come when the present problem of Israel's exclusion from the salvation of the Messias will cease to exist because of her conversion, which will follow the conversion of the Gentiles.  The final conversion of Israel could not be known to St. Paul from any natural source." 

Venerable Bede, Commentary on Psalm 58, etc.
St. Anselm, Commentary on the Epistle to the Romans, Chap. II ;
St. Peter Damian, Sermon 66.
St. Bernard, Letter 363
St. Thomas Aquinas, Commentary on the Epistle to the Romans, Chapter XI, 4
Suarez, Sermon 66
Tertullian, L. V, contra Marcion, Chap.IX ;
Origen, Sixth Homily on the Book of Numbers, towards the end.
St. Hilary, Commentary on Psalm 58 ;
St. Ambrose, Book about the Patriarch Joseph.
St. John Chrysostom, Commentary on the Epistle to the Romans, Chap. XI;
St. Jerome, Commentary on Micheas, Chap. II; Commentary on Malachias, Chap. III, etc.;
St Cyril of Alexandria, Commentary on Genesis, Book, V, etc.;
St. Prosper of Aquitaine, The Calling of the Gentiles, Book I, Chap. XXI. Cassiodorus, Commentary on Psalm 102;
Preniasius, Commentary on the Epistle to the Romans, Chap.XI.
St. Gregory the Great, Liber Moralium, lib. II, etc.;
St. Isidore, Book about the Calling of the Gentiles, Chap. V.