And when Abram was ninety years old and nine (Gen. 17:1). May it please our master to teach us whether a man is permitted to heal a wound on the Sabbath? Thus did our masters teach us: Whenever life is endangered, the Sabbath is superseded. For example, circumcision and its healing supersede the Sabbath. [Yoma 73a; Buber Tanhuma, Lekh Lekha 21. Cf. Bereshit Rabbah, Ha’azinu—One may heal an earache on the Sabbath.]
R. Yosé stated: See how beloved is the precept concerning circumcision, that it supersedes even the Sabbath, as it is written: And on the eighth day, the flesh of his foreskin shall be circumcised (Lev. 12:3), even on the Sabbath. Since circumcision endangers life, one is permitted to heal it on the Sabbath.
When the Holy One, blessed be He, told Abraham: Walk before Me, and be thou wholehearted (Gen. 17:1), Abraham began to wonder. He said to himself: “Surely, until now I have been whole in body, but if I circumcise myself I shall be incomplete. There are five prepuces, four in a man and one on a tree. The prepuce of the ear, as it is written: Behold, their ear is uncircumcised (Jer. 6:10); the prepuce of the heart, as it is written: Remove the obduracy of your heart (Deut. 10:16); the prepuce of the tongue, as it is said: Of uncircumcised lips (Exod. 6:12); the prepuce of the flesh, as it is written in this verse: Ye shall be circumcised in the flesh of your foreskin (Gen. 17:1). If I should circumcise any one of these prepuces, my organs will be incomplete.” The Holy One, blessed be He, asked him: “Why do you believe that you are whole? In fact you lack five limbs. Before you were circumcised, your name was Abram: The alef in your name is one, the bet two, the resh two hundred, and the mem forty, and that totals two hundred and forty-three. However, Man’s limbs total two hundred and forty-eight. Circumcise yourself and you will be whole.” After he was circumcised, the Holy One, blessed be He, said to Him: No longer is your name Abram; henceforth it will be Abraham (ibid., v. 5). He added a heh, which equals five, to his name, making a total of two hundred forty-eight, corresponding to the number of limbs in the human body. Hence Scripture says: Be thou whole.