When Abraham was ninety-nine years old, G-d commanded Abraham to circumcise himself.
G-d told Abraham, "As long as you are uncircumcised, you are imperfect. By performing circumcision you will achieve a new degree of holiness and will be elevated above the laws of nature. For twenty generations I have waited for you to come and perform circumcision.. If you refuse to perform this commandment, I shall return the world to nothingness."
"If the commandment of circumcision is so great," asked Abraham, "Why did You not give it to the first man Adam?
"Do not question me any further," G-d said. You are the one who was found worthy of this commandment.
Abraham objected, "Until now I was able to influence people. But now, they will be afraid of approaching me. They will not want to perform circumcision."
"Do not worry about it. Let it suffice for you that I shall be your G-d. You will not lose out. By performing the commandment of circumcision, you will maintain the existence of this world. I shall enter into a covenant with you in the merit of this commandment.. By observing it, your children, will inherit the Land of Israel."
G-d commanded, "The commandment of circumcision shall be observed by all your descendants. Every newborn male shall be circumcised on the eighth day after his birth."
G-d departed from Abraham who then went to consult his students, Aner, Eshkol, and Mamrai about the commandments of circumcision.
Aner answered, "You must circumcise yourself secretly, or else the relatives of the kings whom you slew will hear of it and come to attack you!" Eshkol advised, "Do not circumcise yourself at all! It is a dangerous operation in ones old age, and you might lose so much blood it might prove fatal!" Abraham heeded neither of them and asked Mamrai for his opinion. "G-d saved you miraculously for the fiery furnace," answered Mamrai.. He saved you from the kings in a supernatural manner. Why do you hesitate to perform circumcision in public?"
G-d rewarded Mamrai for his sagacious words by later appearing to Abraham on Mamrai's property, Elonai Mamrei.
"Who shall perform circumcision on me?" Abraham questioned G-d.
"You yourself," was the answer. Abraham took the knife and was afraid. He was an old man and his arm trembled. "I am old," he said to G-d. G-d then seemingly stretched out His arm and seized the instrument together with Abraham until the circumcision was completed.
Abraham circumcised himself in broad daylight and on the same day also circumcised his household, three hundred and eighteen men, not counting his slaves. His righteous students, Aner, Eshkol, and Mamrai were among those that were circumcised. Abraham's son Ishmael, was thirteen years old when Abraham circumcised him, yet he allowed his father to perform circumcision on him without objecting.
As a result of Ishmael's allowing his father to circumcise him even though he was already thirteen years of age, his descendants rose to great and powerful heights in history.
* Adapted from the book: The Midrash Says, with permission from the publisher