Verse 21: Was not Abraham our father justified by works, (Gen. 22:9, 12) when he had offered Isaac his son upon the altar?
[Abraham our faither] Father, either, 1. of the Jews (Estius, thus Grotius), according to the flesh (Grotius): or, 2. of all believers, for whom he is pattern and a kind of prototype of justification (Estius); father of faith and righteousnss (Menochius).
Was not Abraham our father; not only the father of us as Jews, (for to them he wrote,) and according to the flesh, but as believers, and according to the promise; so all believers are called Abraham’s children, Romans 4:11; Galatians 3:7.
[Was he not justified by works] That is to say, But if that faith of Abraham, already made known in Genesis 15:6, was indeed profitable, but not alone; why should others promise to themselves more from their inoperative faith? Abraham, if he had believed faith to be sufficient to conciliate and retain the favor of God for himself, would have refrained from so grievous a work, concerning which this Writer now will speak (Grotius).
Justified by works; found or declared to be justified, not only before God, but in the face of the world; and his faith (by which he had been justified above thirty years before in the sight of God) now approved as a true, lively, justifying faith, by this proof he gave of it, upon God’s trying him in the offering up his son, Genesis 22:9, 12, Now I know that thou fearest God, etc. Abraham did fear God, and believe him before, and was justified before in the sight of God; but by the working of his faith in so eminent an act of obedience, the sincerity of all his graces, and so of his faith, was manifested and made known, and so his faith itself justified, as his person was before, and he obtained this ample testimony from the mouth of God himself. So that Abraham’s justification here was not the absolution of a sinner, but the solemn approbation of a believer; not a justifying him as ungodly, but commending him for his godliness. He was by his works justified as a righteous person, but not made righteous, or constituted in a justified state, by his works. The design of the apostle is not to show how sinners are justified in God’s court, but only what kind of faith it is whereby they are justified, viz. such a one as purifies the heart, Acts 15:9, and looks to Christ, not only as made righteousness, but sanctification to them, 1 Corinthians 1:30; and consequently not only rests on him for justification, but stirs them up to yield obedience to him.
[Offering, etc., ἀνενέγκας, etc.] When he had offered (that is, he had willed to offer [Estius], had prepared himself to offer [Estius, similarly Menochius], and it was not due to him that he did not offer him [Menochius, Grotius]: This preparation, in which nothing was wanting except the deadly blow, brings it to pass that he obtains from God the praise as of a thing accomplished, Genesis 22:12: Compare Hebrews 11:17 [Grotius]: As far as it pertains to the performance of the heart, he sacrificed him [Grotius out of Salvian]) Isaac his son (that is, his only son of his dearest wife, begotten in their old age [Grotius]) upon the altar? (Erasmus, Beza, Piscator). With significance does he add this from Genesis 22:9, that is to say, unto certain, as he believes, death, which was wont to follow sacrificial victims thus being place upon the altar, and being bound to it (according to custom, concerning which see Virgil concerning Sinon, and Ovid’s From the Black Sea 2) (Grotius).
When he had offered Isaac his son; viz. in his firm purpose and resolution, and was about to do it actually, had not God hindered him. It was no fault in Abraham that it was not actually done, and therefore it was counted to him as if it had been really done, Genesis 22:12; Hebrews 11:17. Upon the altar; this shows the settled purpose of Abraham to sacrifice Isaac, when he proceeded so far as to bind him, and lay him upon the altar; for that argues, that he expected and intended nothing but his death, which generally was wont to follow in sacrifices when once laid upon the altar.
 Greek: Ἀβραὰμ ὁ πατὴρ ἡμῶν οὐκ ἐξ ἔργων ἐδικαιώθη, ἀνενέγκας Ἰσαὰκ τὸν υἱὸν αὐτοῦ ἐπὶ τὸ θυσιαστήριον;
 Æneid 2. In Virgil’s account of the Trojan War, Sinon is a cunning Greek spy, responsible for convincing the Trojans to take the giant wooden horse into their city. As part of his deception of the Trojans, he tells them that Odysseus had intended to sacrifice him, but he narrowly escaped.
 Ovid (43 BC-17 AD) was a Roman poet.
 Epistulæ ex Ponto.