4 and Abraham circumcised Isaac his son when he was eight days old, as God commanded him.
Genesis 21:4 Cross References - MSTC
Genesis 17:10-12
10 This is my covenant which ye shall keep between me and you and thy seed after thee: that ye circumcise all your men children.
11 Ye shall circumcise the foreskin of your flesh, and it shall be a token of the covenant betwixt me and you.
12 And every manchild when it is eight days old, shall be circumcised among you in your generations, and all servants also born at home or bought with money, though they be strangers and not of thy seed.
Exodus 12:48
48 If a stranger dwell among you, and will hold Passover unto the LORD, let him circumcise all that be males, and then let him come and observe it, and be taken as one that is born in the land. No uncircumcised person shall eat thereof.
Leviticus 12:3
3 And in the eighth day the flesh of the child's foreskin shall be cut away.
Deuteronomy 12:32
32 But whatsoever I command you, that take heed ye do: and put nought thereto, nor take ought therefrom.
Luke 1:6
6 Both were perfect before God, and walked in all the laws and ordinances of the Lord, that no man could find fault with them.
Luke 1:59
59 And it fortuned, the eighth day they came to circumcise the child: and called his name Zacharias after the name of his father,
Luke 2:21
21 And when the eighth day was come that the child should be circumcised, his name was called Jesus, which was named of the angel before he was conceived in the mother's womb.
John 7:22-23
22 Moses therefore gave unto you circumcision: not because it is of Moses, but of the fathers. And yet ye on the Sabbath day circumcise a man.
23 If a man on the Sabbath day receive circumcision without breaking of the law of Moses: Disdain ye at me, because I have made a man every whit whole on the Sabbath day?
Acts 7:8
8 And he gave him the covenant of circumcision, and he begat Isaac, and circumcised him the eighth day, and Isaac begat Jacob, and Jacob the twelve patriarchs.