The interpretation timeline
Isaiah 43:21 Douay-Rheims

This people have I formed for myself, they shall shew forth my praise.

A.D. 202 – 1871 6 witnesses

Patristic

before A.D. 750
202
A.D.
Irenaeus Patristic
c. A.D. 130–202
“And those of them who declare that God would make a new covenant with men, not such as that which He made with the fathers at Mount Horeb, and would give to men a new heart and a new spirit; and again, "And remember ye not the things of old: behold, I make new things which shall now arise, and ye shall know it; and I will make a way in the desert, and riven in a dry land, to give drink to my chosen people, my people whom I have acquired, that they may show forth my praise," -plainly announced that liberty which distinguishes the new covenant, and the new wine which is put into new bottles, [that is], the faith which is in Christ, by which He has proclaimed the way of righteousness sprung up in the desert, and the streams of the Holy Spirit in a dry land, to give water to the elect people of God, whom He has acquired, that they might show forth His praise, but not that they might blaspheme Him who made these things, that is, God.”
Source

Scholastic

c. 1100 – 1500
1105
A.D.
Rashi Jewish
1040–1105
“This people I formed for Myself so that they recite My praise.”
1167
A.D.
Ibn Ezra Jewish
1089–1167
זה = זו This. This people, that returns from Babylon, is mine.”
1256
A.D.
Thomas Aquinas Catholic
1225–1274
“And now thus says the Lord, etc. Here he shows them the divine love through the remedies which he granted them amid their distresses. And it is divided into three parts. In the first he promises future remedies, to show his love; in the second he recalls past benefits, to confirm the promise: "thus says the Lord, who gave," etc.; in the third he excludes merits, to take away presumption: "you did not call upon me," etc. Concerning the first he does three things. First he shows toward them the privilege of divine love; second, from the promised remedies, he excludes any partnership in divine power: "all the nations are gathered together," etc.; in the third he sets forth the sign of his love: "thus says the Lord your redeemer," etc. Concerning the first, he promises them three remedies. First, sustenance in punishments, excluding fear by the divine presence: "creating you" — as to the principles of substance, Deut. 32: "he is your father," etc.; "forming" — as to the form which he gave, Gen. 1: "the Lord formed," etc.; "redeeming" — from evils, Hosea 13: "from the hand of death," etc.; and "I have called" — unto grace, Hosea 1: "I will call 'not my people,'" etc. He sets forth the promise: "when you shall pass through the waters" — the Egyptians; "the rivers" — the Chaldeans; "the fire" — the Greeks; "the flame" — the Romans. For they were not consumed entirely. Ps. 65: "we passed through fire," etc. And he assigns the reason for this: "for I am the Lord," etc., above, 12: "for he himself, God, is savior," etc. Second, he promises a commutation of punishments, namely that he will punish others in his place. And he sets forth the commutation. "I have given a propitiation" — that is, that I might be propitiated toward you, as it were by the punishments of those who provoked you to sin by the hope of their help. "Saba" — a city of Ethiopia. Prov. 11: "the just man out of distress," etc. And he assigns the reason, namely God's own love: "since you have become honorable" — that is, I have made and accounted you honorable. "For you" — for your liberation. Jer. 31: "if a son honorable to me," etc. Third, he promises them liberation of every kind from tribulations; and concerning this, three things. First he promises the benefit of liberation: "do not fear, from the east" — because they had been scattered in every direction. Above, 11: "he will gather the fugitives," etc.; Jer. 31: "behold I will bring them," etc. Second, he sets forth the merit of liberation: "and everyone who calls upon me I will bring" — "unto my glory," that he may glorify me, and I may appear glorious in him. Joel 2: "everyone whosoever shall call upon," etc. Third, he promulgates the precept of liberation. "Bring forth," O Cyrus, "outside" — outside the land of captivity — "the people," namely of the Jews. Jer. 5: "hear, foolish people," etc. "All the nations." Here he excludes any partnership in godhead. And first he shows the falsity of the other gods by way of a judgment, setting forth the nations' agreement with idols: "are gathered together" — into one error. Ps. 13: "all have gone astray," etc. — seeking a sign of godhead. "Who among you" — that is, which of your gods? Or he speaks to the idols, and seeks testimony. "Let them give witnesses," and "let them be justified" — that is, let them be justly called gods; and let the witnesses hear future things from them, and speak testimony on your behalf. Above, 41: "there is none announcing nor foretelling," etc. Second, he shows the truth of his own godhead: and first as to knowledge; second as to power, "you are witnesses," etc. Concerning the first, two things. First he gives testimony, assigning men as witnesses: "truly you are witnesses," etc.; "my servant" — the people of Jacob, or Christ. Acts 1: "you shall be witnesses to me," etc.; setting forth the manner of knowing: "that you may know" — as to those things which can be known of God through natural reason; and "that you may believe" — as to those things which are above reason; and thus "you may understand": for unless you shall have believed, you shall not understand, above, 8, according to another text. He also sets forth the saying of the witnesses, that he alone is God: "for I alone" — "I am" — "God." "The one who forms," or "the one formed" — namely, an idol — Deut. 32: "see that I am he alone," etc.; and that he alone is Lord: "I am" — singularly; "I am" — excellently, etc.; Acts 4: "there is no salvation in any other," etc. Second he gives a sign of godhead. "I have announced," etc.; "there was not" one from whom you could know. Ps. 80: "Israel, if you will hear me," etc. "You are witnesses," etc. Here he shows the truth of his godhead as to power: and first he gives testimony, "you are witnesses," etc., John 8: "I am the beginning," etc. Second he gives a sign of power in punishing: "and there is none who" out of the "hand" — as Deut. 32, Job 10; and in working, "I will work," etc., above, 14: "the Lord of hosts has decreed," etc. "Thus says the Lord," etc. Here he sets forth the sign of love: because for their sake he destroyed the Babylonians glorying in their ships, on account of the multitude of waters. "I have sent forth" — namely, wrath — Jer. 51: "the Lord has planned and has done," etc. "Thus says the Lord who gave," etc. Here he recalls past benefits, to confirm hope concerning future ones. And concerning this he does two things. First he recalls the past benefits when they went out from Egypt, in their governance. "In the sea" — the Red Sea, Exod. 14; "in the waters of the torrent" — in the Arnon, Numbers 21; in the Jordan, Joshua 3. And as to the destruction of enemies: "who brought forth the chariot" — the chariots of Pharaoh, etc., Exod. 15: "his chosen princes," etc.; "as flax" — cut off in a moment. Second he promises things much greater in the future; and concerning this he does three things. First he shows the greatness of future benefits by comparison with the former: "do not remember" — as if to say: they are not worthy to be held in memory in comparison with the future ones, Phil. 3: "forgetting indeed those things which are behind," etc.; by their newness: "behold I make new things" — unheard of, Apoc. 21: "behold I make all things new." And by their determination: "I will set in the desert" — that is, in the land of the Jews, which was formerly desert — "a way" — of those going to the festivities; "rivers" — of consolation, Ps. 106: "he turned the desert into pools," etc. And if these things are expounded literally of the liberation from the captivity of Babylon, they are said to be greater than the liberation from Egypt — not on account of greater miracles, but because the kings from whose power he liberated them were more powerful than Pharaoh; or because they came from a more distant place. But if they are referred to the liberation wrought through Christ, it is clear that nothing so admirable had preceded it in past ages. Second he shows the usefulness of the benefits among the nations: "and the beast of the field will glorify" — that is, the Gentile living beastially, converted to Christ; or those seeing how I free the Jews. Ps. 148: "beasts and all cattle," etc.; and among the Jews: "that I might give drink" — of doctrine and consolation, Deut. 7: "the Lord has chosen you," etc. Third he assigns the reason: "this people for myself" — unto my praise. Prov. 16: "all things for himself," etc. "You did not call upon me." Here he excludes the merits of the Jews for obtaining such great benefits; and concerning this, three things. First he excludes merit; second he gives room for a response, "bring me back to mind," etc.; third he removes a certain manner of responding, "your father," etc. Concerning the first, three things. First he excludes merit: "you did not call upon me" — and all these things are said because they did not offer these things to God with their whole heart, but partly to God, partly to idols; or because they conferred nothing on God; or because they did them in hope of temporal recompense; or because after the coming of Christ they were not accepted. Mal. 3: "who is there among you that would shut the doors," etc.; Ps. 49: "shall I eat," etc. Second he shows their guilt: "nevertheless, to serve" — as if to say: you have shown me servile, while, though you offended me, I did not punish. Above, 1: "they have become troublesome to me," etc. He speaks in a human manner. Third he shows the benefit given freely: "I am," etc., Ps. 24: "for your name's sake you will be propitious," etc., Ez. 36: "not for your sakes will I do this," etc. "Bring me to remembrance," etc. Here he gives room for a response. "Bring back" — as if to say: think again on what I have done for you; tell if you have anything, to excuse yourself, or to accuse me, that you may be justified, that is, that you may be judged just. Job 33: "if you have anything to say," etc. "Your father." Here he removes a certain way of responding. For they could allege the innocence of their fathers; but against this he speaks. "Father" — Adam, Gen. 3; Abraham, seeking a sign concerning God's promise, as though doubting, Gen. 15; "interpreters" — Moses and Aaron at the waters of contradiction, Num. 21; "I have profaned" — that is, I have allowed to be profaned — unto utter destruction: for all died in the desert, except Caleb and Joshua. Ps. 105: "we have sinned with our fathers," etc. (Collationes, chap. 43). The Lord frees the saints from fire: of carnal temptation, Job 31: "it is a fire even unto consumption," etc.; of temporal tribulation, Ps.: "you have tried me by fire"; of eternal damnation, Matt. 25: "depart, you cursed"; of divine indignation, Deut. 32: "a fire is kindled," etc. In which are burned: the lascivious, 1 Cor. 7: "it is better to marry," etc.; the impatient, above, 13: "their faces shall be burnt," etc.; the impenitent, Ps.: "the flame has burned up sinners"; the proud, the same: "the foundations of the mountains," etc. He also frees from waters: of pleasure, Prov. 9: "stolen waters," etc., in which they are suffocated through luxury; of cupidity, Exod. 15: "they sank as lead," etc., in which through avarice; of adversity, Ps.: "the waters have come in even unto the soul," etc., in which through impatience; of worldly power, Apoc. 17: "the waters upon which she sits," etc., in which through pride. Bring God back into memory as to: the wonders which he has done, that they be venerated, Ps.: "remember his wonders," etc.; the benefits which he gave, that thanks be rendered, Ecclus., last chapter: "I have remembered mercy," etc.; the torments which he endured, that compassion be shown, Lam. 3: "remember my poverty," etc.; the precepts which he gave, that they be observed, Ps.: "that they may be mindful," etc.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“But thou hast not called upon me, O Jacob,.... The Jews, though they were the posterity of Jacob, a praying person, yet did not tread in his steps, but were more like the Heathens that called not on the name of the Lord; though there is no necessity of restraining this to prayer, it may regard the whole worship of God, which is sometimes included in the invocation of his name; and so the Targum, "and ye come not to my worship, O ye of the house of Jacob.'' The Jews, in Christ's time, did not call upon his name, nor believe in him, nor receive his Gospel, nor submit to him and his ordinances; they rejected him and his service, therefore the Lord rejected them, and called the Gentiles, as before prophesied of: but thou hast been weary of me, O Israel: of the word, worship, and ordinances of God; see Mal 1:13.”
Source
1871
A.D.
1871
“This people--namely, The same as "My people, My chosen" (see Isa 43:1, Isa 43:7; Psa 102:18). my praise--on account of the many and great benefits conferred on them, especially their restoration.”
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.