Exodus 12:48 "But if a stranger sojourns with you, and celebrates the Passover to the LORD, let all his males be circumcised, and then let him come near to celebrate it; and he shall be like a native of the land. But no uncircumcised person may eat of it.

Deuteronomy 10:16 "So circumcise your heart, and stiffen your neck no longer.

Acts 7:8 "And He gave him the covenant of circumcision; and so Abraham became the father of Isaac, and circumcised him on the eighth day; and Isaac became the father of Jacob, and Jacob of the twelve patriarchs.

Romans 4:11 and he received the sign of circumcision, a seal of the righteousness of the faith which he had while uncircumcised, so that he might be the father of all who believe without being circumcised, that righteousness might be credited to them, (NASB ©1995)