4 Abraham circumcised his son, Isaac, when he was eight days old, as God had commanded him.
Genesis 21:4 Cross References - NHEB
Genesis 17:10-12
10 This is my covenant, which you shall keep, between me and you and your descendants after you: Every male among you shall be circumcised.
11 You shall be circumcised in the flesh of your foreskin. It will be a sign of the covenant between me and you.
12 He who is eight days old will be circumcised among you, every male throughout your generations, he who is born in the house, or bought with money from any foreigner who is not of your descendants.
Exodus 12:48
48 When a stranger shall live as a foreigner with you, and will keep the Passover to the LORD, let all his males be circumcised, and then let him come near and keep it; and he shall be as one who is born in the land: but no uncircumcised person shall eat of it.
Leviticus 12:3
3 In the eighth day the flesh of his foreskin shall be circumcised.
Deuteronomy 12:32
32 Whatever thing I command you, that you shall observe to do: you shall not add thereto, nor diminish from it.
Luke 1:6
6 They were both righteous before God, walking blamelessly in all the commandments and ordinances of the Lord.
Luke 1:59
59 It happened on the eighth day, that they came to circumcise the child; and they would have called him Zechariah, after the name of the father.
Luke 2:21
21 When eight days were fulfilled to circumcise him, his name was called Jesus, which was given by the angel before he was conceived in the womb.
John 7:22-23
Acts 7:8
8 He gave him the covenant of circumcision. So Abraham became the father of Isaac, and circumcised him the eighth day. Isaac became the father of Jacob, and Jacob became the father of the twelve patriarchs.