20 Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
[AD 407] John Chrysostom on Romans 9:22-23:24
What he means is somewhat as follows. Pharaoh was a vessel of wrath, that is, a man who by his own hard-heartedness had kindled the wrath of God. For after enjoying much long-suffering, he became no better, but remained unimproved. Wherefore he calls him not only "a vessel of wrath," but also one "fitted for destruction." That is, fully fitted indeed, but by his own proper self. For neither had God left out anything of the things likely to recover him, nor did he leave out anything of those that would ruin him, and put him beyond any forgiveness. Yet still, though God knew this, "He endured him with much long-suffering," being willing to bring him to repentance. For had He not willed this, then He would not have been thus long-suffering. But as he would not use the long-suffering in order to repentance, but fully fitted himself for wrath, He used him for the correction of others, through the punishment inflicted upon him making them better, and in this way setting forth His power. For that it is not God's wish that His power be so made known, but in another way, by His benefits, namely, and kindnesses, he had shown above in all possible ways. For if Paul does not wish to appear powerful in this way ("not that we should appear approved," he says, "but that you should do that which is honest,") [2 Corinthians 13:7], much less does God. But after that he had shown long-suffering, that He might lead to repentance, but he did not repent, He suffered him a long time, that He might display at once His goodness and His power, even if that man were not minded to gain anything from this great long-suffering. As then by punishing this man, who continued incorrigible, He showed His power, so by having pitied those who had done many sins but repented, He manifested His love toward man. But it does not say, love towards man, but glory, to show that this is especially God's glory, and for this He was above all things earnest. But in saying, "which He had afore prepared unto glory," he does not mean that all is God's doing. Since if this were so, there were nothing to hinder all men from being saved. But he is setting forth again His foreknowledge, and doing away with the difference between the Jews and the Gentiles. And on this topic again he grounds a defense of his statement, which is no small one. For it was not in the case of the Jews only that some men perished, and some were saved, but with the Gentiles also this was the case. Wherefore he does not say, all the Gentiles, but, "of the Gentiles," nor, all the Jews, but, "of the Jews." As then Pharaoh became a vessel of wrath by his own lawlessness, so did these become vessels of mercy by their own readiness to obey. For though the more part is of God, still they also have contributed themselves some little. Whence he does not say either, vessels of well-doing, or vessels of boldness (παρρησίας), but "vessels of mercy," to show that the whole is of God. For the phrase, "it is not of him that wills, nor of him that runs," even if it comes in the course of the objection, still, were it said by Paul, would create no difficulty. Because when he says, "it is not of him that wills, nor of him that runs," he does not deprive us of free-will, but shows that all is not one's own, for that it requires grace from above. For it is binding on us to will, and also to run: but to confide not in our own labors, but in the love of God toward man. And this he has expressed elsewhere. "Yet not I, but the grace which was with me." [1 Corinthians 15:10] And he well says, "Which He had afore prepared unto glory." For since they reproached them with this, that they were saved by grace, and thought to make them ashamed, he far more than sets aside this insinuation. For if the thing brought glory even to God, much more to them through whom God was glorified. But observe his forbearance, and unspeakable wisdom. For when he had it in his power to adduce, as an instance of those punished, not Pharaoh, but such of the Jews as had sinned, and so make his discourse much clearer, and show that where there were the same fathers, and the same sins, some perished, and some had mercy shown them, and persuade them not to be doubtful-minded, even if some of the Gentiles were saved, while the Jews were perishing; that he might not make his discourse irksome, the showing forth of the punishment he draws from the foreigner, so that he may not be forced to call them "vessels of wrath." But those that obtained mercy he draws from the people of the Jews. And besides, he also has spoken in a sufficient way in God's behalf, because though He knew very well that the nation was fitting itself as a vessel of destruction, still He contributed all on His part, His patience, His long-suffering, and that not merely long-suffering, but "much long-suffering;" yet still he was not minded to state it barely against the Jews. Whence then are some vessels of wrath, and some of mercy? Of their own free choice. God, however, being very good, shows the same kindness to both. For it was not those in a state of salvation only to whom He showed mercy, but also Pharaoh, as far as His part went. For of the same long-suffering, both they and he had the advantage. And if he was not saved, it was quite owing to his own will: since, as for what concerns God, he had as much done for him as they who were saved. Having then given to the question that answer which was furnished by facts, in order to give his discourse the advantage of other testimony in its favor, he introduces the prophets also making the same declarations aforetime. For Hosea, he says, of old put this in writing, as follows:

[AD 253] Origen of Alexandria on Romans 11:20
Who is the one from whom they have been broken off but he in whom they have not believed?

[AD 258] Cyprian on Romans 11:20
But I hear that some infect your number, and destroy the praise of a distinguished name by their corrupt conversation; whom you yourselves, even as being lovers and guardians of your own praise, should rebuke and check and correct. For what a disgrace is suffered by your name, when one spends his days in intoxication and debauchery, another returns to that country whence he was banished, to perish when arrested, not now as being a Christian, but as being a criminal! I hear that some are puffed up and are arrogant, although it is written, "Be not high-minded, but fear: for if God spared not the natural branches, take heed lest He also spare not thee." Our Lord "was led as a sheep to the slaughter; and as a lamb before her shearers is dumb, so He opened not His mouth." "I am not rebellious," says He, "neither do I gainsay. I gave my back to the smiters, and my cheeks to the palms of their hands. I hid not my face from the filthiness of spitting." And dares any one now, who lives by and in this very One, lift up himself and be haughty, forgetful, as well of the deeds which He did, as of the commands which He left to us either by Himself or by His apostles? But if "the servant is not greater than his Lord." let those who follow the Lord humbly and peacefully and silently tread in His steps, since the lower one is, the more exalted be may become; as says the Lord, "He that is least among you, the same shall be great."

[AD 258] Cyprian on Romans 11:20
That humility and quietness are to be maintained in all things. In Isaiah: "Thus saith the Lord God, The heaven is my throne, and the earth is the stool of my feet. What seat will ye build for me, or what is the place for my rest? For all those things hath my hand made, and all those things are mine. And upon whom else will I look, except upon the lowly and quiet man, and him that trembleth at my words? " On this same thing in the Gospel according to Matthew: "Blessed are the meek, for they shall inherit the earth." Of this same thing, too, according to Luke: "He that shall be least among you all, the same shall be great." Also in the same lace: "Whosoever exalteth himself shall be made low, and whosoever abaseth himself shall be exalted." Of this same thing to the Romans: "Be not high-minded, but fear; for if God spared not the natural branches, (take heed) lest He also spare not thee." Of this same thing in the thirty-third Psalm: And He shall save the lowly in spirit." Also to the Romans: "Render to all what is due: tribute to whom tribute is due, custom to whom custom, fear to whom fear, honour to whom honour; owe no man anything, except to love another." Also in the Gospel according to Matthew: "They love the first place of reclining at feasts, and the chief seat in the synagogues, and salutations in the market, and to be called of men Rabbi. But call not ye Rabbi, for One is your Master." Also in the Gospel according to John: "The servant is not greater than his lord, nor the apostle greater than He that sent himself. If ye know these things, blessed shall ye be if ye shall do them." Also in the eighty-first Psalm: "Do justice to the poor and lowly."

[AD 384] Ambrosiaster on Romans 11:20
You ought to thank God for his gift in Christ and not insult them but rather pray that, if their wickedness has led to your salvation, they too might return to their roots. Then you will please God who has shown you mercy, for he called you so that by making them jealous of you he might bring them to grace as well.

[AD 407] John Chrysostom on Romans 11:20
So here another encomium, and for the other party an accusation. But he again lays their pride low by proceeding to say, "be not high-minded, but fear." For the thing is not matter of nature, but of belief and unbelief. And he seems to be again bridling the Gentile, but he is teaching the Jew that it is not right to cling to a natural kinsmanship. Hence he goes on with, "Be not high-minded," and he does not say, but be humble, but, fear. For haughtiness genders a contempt and listlessness. Then as he is going into all the sorrows of their calamity, in order to make the statement less offensive, he states it in the way of a rebuke given to the other as follows:

[AD 407] John Chrysostom on Romans 11:20
It was not God who cut them off but rather they broke themselves off and fell.… You see what a great thing man’s free choice is, how great the working of the mind is. For none of these things is immutable, neither your good nor their evil.

[AD 418] Pelagius on Romans 11:20
Some interpreters, who do not understand this passage and do not consider the reason for which or the people to whom the apostle is speaking, think that the pursuit of wisdom is forbidden by this text. But if this is so Paul will seem to contradict himself in the eyes of these interpreters, since here he is forbidding what elsewhere he asks of the Lord, that the Ephesians and others may receive.