Exodus 12:48

12:48 “When a foreigner lives with you and wants to observe the Passover to the Lord, all his males must be circumcised, and then he may approach and observe it, and he will be like one who is born in the land – but no uncircumcised person may eat of it.

Exodus 28:43

28:43 These must be on Aaron and his sons when they enter to the tent of meeting, or when they approach the altar to minister in the Holy Place, so that they bear no iniquity and die. It is to be a perpetual ordinance for him and for his descendants after him.