Genesis 17: 26-27 - Note the command of Abraham.

In the selfsame day was Abraham circumcised, and Ishmael his son. And all the men of his house, born in the house, and bought with money of the stranger, were circumcised with him.

Within one day, Abraham was able to order and carry out the circumcision of all the males of his household exactly as God commanded. Being able to command with such authority, Abraham was able to keep the way of the LORD for his household, to do justice and judgment (parallel passage Genesis 18:19).