Ambrose of Milan

And because he is called to what is perfect, Abraham receives the oracle that summons to perfection. "Circumcise," it says, "every male of yours and circumcise your flesh"; but perfect circumcision is the spiritual one. Indeed, Scripture also teaches this when it says, "Circumcise the hardness of your heart." Even here many interpret the text to be saying, "Circumcise every male of yours," that is, your minds; for nothing is more virile than the mind. …

On Abraham ↗

Bede

A child of eight days shall be circumcised among you. For on the eighth day, that is, after the Sabbath, the Lord rose from the dead, in whose passion and resurrection we are baptized, absolved from the oldness of faults, as if we are renewed by spiritual circumcision; the Apostle explaining and saying: For as many of us as were baptized into Christ Jesus were baptized into His death, therefore we were buried with Him through baptism into death: so that just as Christ was raised from the dead by the glory of the Father, so we also …

Commentary on Genesis (Hexaemeron) ↗