John Chrysostom

"For circumcision verily profiteth, if thou keep the Law." And yet, were this not so, a man might have rejected it and said, What is circumcision? for is it any good deed on his part that hath it? is it any manifestation of a right choice? For it takes place at an unripe age, and those in the wilderness too remained uncircumcised for a long time. And from many other points of view also, one might look at it as not necessary. And yet it is not on this foot that he rejects it, but upon the most proper ground, from the case of Abraham. …

Homily on Romans 6 ↗

Theophylact of Ohrid

Since circumcision was held in great esteem among the Jews, he did not say about it immediately at the beginning that circumcision is superfluous and useless, but in words he allows it, while in deed he rejects it, and says: I agree that circumcision is profitable, but only when you fulfill the law. …

Commentary on Romans ↗

Augustine of Hippo

The apostle did not say this as if he favored forcing either the Gentiles to remain uncircumcised or the Jews not to adhere to the traditions of their fathers. Rather, he urged that neither group should be forced into the practice of the other but that each person should have the right, not the obligation, to adhere to his own custom.

On Lying 5.8 ↗

Thomas Aquinas

Then when he says circumcision, he shows that circumcision is not sufficient for salvation any more than the law is, and for the same reason, namely, that without circumcision there is value in the law's observance, without which circumcision has no benefit, as was said above. In regard to this he does three things. First, he compares circumcision to the circumcised Jews; second, to the uncircumcised gentiles, at if then, the uncircumcised; third, he explains what he had said, at for he is not a Jew who is so outwardly. …

Commentary on Romans ↗