Matthew Poole and continuators on 1 Corinthians 7:18

18 Is any man called being circumcised? let him not become uncircumcised: Is any called in uncircumcision? let him not become circumcised .

Is any one who was a native Jew, and so circumcised according to the Jewish Law converted (while he is in that state) to the Faith of Christ, let him not affect the state of him, that having been formerly a Gentile, was never circumcised. On the other side, is any, being a native Gentile, and so not circumcised, converted to Christianity, let not him affect the state of one converted from Judaism, who was circumcised. This is doubtless the sense of the verse, not (as some would have it) let him not endeavour by art to make himself uncircumcised, which was the wicked practice of some (for a better compliance with the Gentiles) of whom we read, 1 Maccab. 1.17.