Thomas Aquinas, on Gal 3:7

“Know ye therefore, that they who are of faith, the same are the children of Abraham.”

“From this authority he draws the minor proposition, saying "Know ye therefore, that they who are of faith, the same are the children of Abraham." As if to say: Someone is called the son of another because he imitates his works; therefore, "if you be the children of Abraham, do the works of Abraham" (Jn 8:39). But Abraham did not seek to be justified through circumcision but through faith. Therefore the sons of Abraham are they who seek to be justified by faith. And this is what he says: Because Abraham is just through faith, in that he believed God and it was reputed to him unto justice; "therefore, know ye that they" who are of faith, i.e., who believe that they are justified and saved by faith, "the same are the children of Abraham," namely, by imitation and instruction: "They that are the children of the promise are accounted for the seed" (Rom 9:8); "This day is salvation come to this house, because he also is the son of Abraham" (Lk 19:9); "God is able of these stones," i.e., of the Gentiles, "to raise up children to Abraham," inasmuch as He makes them believers (Mt 3:9).”

Imported from an open dataset — not yet checked against the printed edition.