Genesis 17:10-14

17:10 This is my requirement that you and your descendants after you must keep: Every male among you must be circumcised. 17:11 You must circumcise the flesh of your foreskins. This will be a reminder of the covenant between me and you. 17:12 Throughout your generations every male among you who is eight days old must be circumcised, whether born in your house or bought with money from any foreigner who is not one of your descendants. 17:13 They must indeed be circumcised, whether born in your house or bought with money. The sign of my covenant will be visible in your flesh as a permanent reminder. 17:14 Any uncircumcised male who has not been circumcised in the flesh of his foreskin will be cut off from his people – he has failed to carry out my requirement.”

Genesis 17:26-27

17:26 Abraham and his son Ishmael were circumcised on the very same day. 17:27 All the men of his household, whether born in his household or bought with money from a foreigner, were circumcised with him.