And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also:
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Ambrosiaster
AD 400
Abraham received circumcision as a sign of the righteousness of faith. For believing that he would have a son, he received the sign of the thing which he believed, that it might be known that he was justified because of what he believed. Circumcision has no special value; it is just a sign. The children of Abraham received this sign so that it would be known that they were the children of him who had received this sign because he believed in God and so that they would imitate their father’s faith and believe in Jesus, who was promised to Abraham. Isaac was born as a type of Christ, for the nations are not blessed in Isaac but in Christ, “for there is no other name under heaven given among men by which we must be saved,” says the apostle Peter. Commentary on Paul’s Epistles.
And he received, after he was justified, circumcision, as a seal of the justice of faith, which he had before when he believed. Circumcision, therefore, in Abraham, was as a seal and testimony of the justice which he had already by faith: though circumcision was chiefly given to Abraham and his posterity, as a sign or seal of that alliance which God made with Abraham, and his seed, to show he had made choice of them for his elect people. (Witham)
Thou seest how the holy Virgin has surpassed even the perfection of the patriarchs, and how she confirms the covenant which was made with Abraham by God, when He said, "This is the covenant which I shall establish between me and thee."
See how the uncircumcised had Abraham as their father before the circumcised came into existence! So if circumcision must be honored because it preaches righteousness, uncircumcision is still preeminent, because it came before circumcision in the dispensation of faith.
Paul taught us both that Abraham received circumcision as a sign and that while he was still uncircumcised he gave evidence of righteousness arising from faith.
Circumcision was given for these three reasons: First, to be a sign of faith; second, to mark out the race of Abraham, and third, to be a sign and symbol of good and wise behavior. It was not given in order to produce righteousness but as a sign and seal of the righteousness which was Abraham’s by faith. .
Nor yet did he observe the Sabbath. For he had "accepted".
Since, also, he deserved for that reason to be called "the father of many nations "whilst we, who are even more like him.
Which (injuriousness and violence) even the father of the faith.
(nations) who, as the fruit of the "faith "which precedes digamy, had to be accounted "sons of Abraham."
But you Jews say that Abraham was circumcised. Yes, but he pleased God before his circumcision, and he did not yet observe the sabbath. For he had accepted circumcision as a sign for that time, not as a prerogative title to salvation.
Having showed that the blessing of forgiveness of sins is obtained not only in circumcision but also in uncircumcision on the ground that Abraham was justified when he was still uncircumcised [n. 339], the Apostle now responds to an objection. For someone could say: If Abraham was justified before circumcision, then he was circumcised without reason and for no purpose. To exclude this objection, he first states that circumcision was not the cause but the sign of righteousness; secondly, he shows what he obtains from this sign, there [v. 11b; n. 344] at that he might be the father; thirdly, how he obtains it, there [v. 12b; n. 345] at who are not merely. 342. In regard to the first he does two things. First, he states that circumcision is a sign: "You shall be circumcised in the flesh of your foreskin and it shall be a sign of the covenant between you and me" (Gen 17:10). Secondly, he shows what it is a sign of, saying: a seal of the justice of faith, i.e., the justice that comes throug...