TSK · Genesis 21:4

This is my requirement that you and your descendants after you must keep: Every male among you must be circumcised.

“When a resident 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.

Idolatry and False Prophets(13:1) You must be careful to do everything I am commanding you. Do not add to it or subtract from it!

On the eighth day they came to circumcise the child, and they wanted to name him Zechariah after his father.

However, because Moses gave you the practice of circumcision(not that it came from Moses, but from the forefathers), you circumcise a male child on the Sabbath.