"And when Abram was ninety years old and nine, the LORD appeared to Abram, and said unto him, I am the Almighty God; walk before me, and be thou perfect. And I will make my covenant between me and thee, and will multiply thee exceedingly. And Abram fell on his face: and God talked with him, saying, As for me, behold, my covenant is with thee, and thou shalt be a father of many nations. Neither shall thy name any more be called Abram, but thy name shall be Abraham; for a father of many nations have I made thee....
This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.... And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. And I will bless her, and give thee a son also of her: yea, I will bless her, and she shall be a mother of nations; kings of people shall be of her.... And all the men of his house, born in the house, and bought with money of the stranger, were circumcised with him" (Gen. 17:10,15,16,27,1-5).
The Lord appeared to him for the fifth time saying, "I am the Almighty God; walk before me, and be thou perfect." All of his resources were now in God. His name Abram, meaning "father of elevation," was changed to Abraham, "father of a great multitude," or "father of many nations," implying the fulfilling of God's promise to Abraham's seed. As Sarai, "my princess," was to be a mother of nations, she became Sarah, or "Princess." Abraham was entering more fully into the enjoyment of faith's maturity and had learned that it was the barren woman who was to be the mother of thousands, for God had said, "Sarah shall have a son." A new name means a new beginning.
"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" (Gen. 17:26,27).
Circumcision (no confidence in the flesh), which included the entire family, followed before the judgment of the world (Gen. 19).