God further said to Abraham, “As for you, you and your offspring to come throughout the ages shall keep My covenant. Such shall be the covenant between Me and you and your offspring to follow which you shall keep: every male among you shall be circumcised. You shall circumcise the flesh of your foreskin, and that shall be the sign of the covenant between Me and you. And throughout the generations, every male among you shall be circumcised at the age of eight days. As for the homeborn slave and the one bought from an outsider who is not of your offspring, they must be circumcised, homeborn and purchased alike. Thus shall My covenant be marked in your flesh as an everlasting pact. And if any male who is uncircumcised fails to circumcise the flesh of his foreskin, that person shall be cut off from his kin; he has broken My covenant.”

The commandment to circumcise: [Parshat] Lekh Lekha [has] one positive commandment, and that is the commandment to circumcise; as it is stated (Genesis 17:10), "This is My covenant which you shall keep, between you and I, and with your descendants after you, circumcise all males." And [the commandment] is repeated in the Order of Eesha ki Tazria, as it is stated (Leviticus 12:3), "And on the eighth day circumcise the flesh of his foreskin." There are many commandments which are repeated in many places in the Torah; and all of them are necessary as the sages explained (Shabbat 132a and Shabbat 135a). And the content of this commandment is that we cut the foreskin that covers the head of the member and then tearing the sorting skin which is below it so that the glans of the member will be exposed. As is known to those that understand, the completion of the form of man comes with the removal of this foreskin which is extraneous. It is from the roots of this commandment [that it is] because God wanted to establish in His nation, that He separated to be called by His name, a permanent sign on their body; to separate them from the other nations in the form of their bodies just like they are separated from them in the form of their souls, the going out and coming in of which are not similar. He established this difference in the 'golden fountain,' because this is the reason for the existence of people, besides being a completion of the physical body as we mentioned. God wanted to complete His plan with the chosen nation. He wanted men to complete the creation of his body, as He did not create him complete from the womb; [so as] to hint to him that just like the completion of the form of his body is through him, so [too] is it in his hand to complete the form of his soul, by refining his actions. The laws of the commandment - upon whom is the circumcision of infants incumbent, as well as the circumcision of slaves, the homeborn (a Canaanite slave that a maidservant gave birth to in the house of a Jew) and those acquired with money (which means a Canaanite slave that was acquired from when he was born), and the difference between them; in which way is Shabbat and holidays pushed off for him; which infant has his circumcision delayed for more than eight days; and its other details - are [all] elucidated in Chapter Nineteen of Shabbat and in Chapter Four of Yevamot. And there in Shabbat, it is elucidated that the one who circumcises recites the blessing, "Blessed are You, Lord our God, King of the universe, who has sanctified us with Your commandments, and commanded us concerning the circumcision." And the father of the child - or the court when there is no father [present] - recites the blessing, "Blessed are You, Lord our God, King of the universe, who has sanctified us with Your commandments, and commanded us to bring him into the covenant of Avraham, our father." And the ones standing there respond, "Just as he had merit for the circumcision, may God let have him merit for the wedding canopy and for good deeds" (see Shulchan Arukh Yoreh Deah 260-266). And [it] is practiced in every place and at all times. And women are not obligated regarding the circumcision of their sons (Kiddushin 29a); just the father - or the court when there is no father [present]. And one who transgresses this commandment and does not circumcise himself when he reaches the category of [those who can receive] punishments - which is thirteen year and a day - [each day, that he transgresses it from when he is grown and does not circumcise himself, violates a positive commandment. And if he dies and was uncircumcised by volition,] he is liable for excision. But the father is not liable for excision for the [lack of] circumcision of his son (Shabbat 133a), but he does transgress a positive commandment. And there is no positive commandment in all of the Torah the negation of which makes one liable for excision besides this and the slaughtering of the Pesach sacrifice (Keritot 2a).

Cut away [i.e. circumcise], therefore, the thickening about your hearts and stiffen your necks no more.

The Sages taught: There was an incident involving one gentile who came before Shammai. The gentile said to Shammai: How many Torahs do you have? He said to him: Two, the Written Torah and the Oral Torah. The gentile said to him: With regard to the Written Torah, I believe you, but with regard to the Oral Torah, I do not believe you. Convert me on condition that you will teach me only the Written Torah. Shammai scolded him and cast him out with reprimand.

The same gentile came before Hillel, who converted him and began teaching him Torah. On the first day, he showed him the letters of the alphabet and said to him: Alef, bet, gimmel, dalet [i.e. A, B, C, D]. The next day he reversed the order of the letters and told him that an alef [A] is a tav [Z[ and so on [i.e. a B is a Y, etc.]. The convert said to him: But yesterday you did not tell me that. Hillel said to him: You see that it is impossible to learn what is written without relying on an oral tradition. Didn’t you rely on me? Therefore, you should also rely on me with regard to the matter of the Oral Torah, and accept the interpretations that it contains.

There was another incident involving one gentile who came before Shammai and said to Shammai: Convert me on condition that you teach me the entire Torah while I am standing on one foot. Shammai pushed him away with the builder’s cubit in his hand. This was a common measuring stick and Shammai was a builder by trade. The same gentile came before Hillel. He converted him and said to him: That which is hateful to you do not do to another; that is the entire Torah, and the rest is its interpretation. Go study.

There was another incident involving one gentile who was passing behind the study hall and heard the voice of a teacher who was teaching Torah to his students and saying the verse: “And these are the garments which they shall make: A breastplate, and an efod, and a robe, and a tunic of checkered work, a mitre, and a girdle” (Exodus 28:4). The gentile said: These garments, for whom are they designated? The students said to him: For the High Priest. The gentile said to himself: I will go and convert so that they will install me as High Priest.

He came before Shammai and said to him: Convert me on condition that you install me as High Priest. Shammai pushed him with the builder’s cubit in his hand. He came before Hillel; he converted him. Hillel said to him, to the convert: Is it not the way of the world that only one who knows the protocols [takhsisei] of royalty is appointed king? Go and learn the royal protocols by engaging in Torah study. He went and read the Bible. When he reached the verse which says: “And the common man that draws near shall be put to death” (Numbers 1:51), the convert said to Hillel: With regard to whom is the verse speaking? Hillel said to him: Even with regard to David, king of Israel. The convert reasoned an a fortiori inference himself: If the Jewish people are called God’s children, and due to the love that God loved them he called them: “Israel is My son, My firstborn” (Exodus 4:22), and nevertheless it is written about them: And the common man that draws near shall be put to death; a mere convert who came without merit, with nothing more than his staff and traveling bag, all the more so that this applies to him, as well. The convert came before Shammai and told him that he retracts his demand to appoint him High Priest, saying: Am I at all worthy to be High Priest? Is it not written in the Torah: And the common man that draws near shall be put to death? He came before Hillel and said to him: Hillel the patient, may blessings rest upon your head as you brought me under the wings of the Divine Presence.

The Gemara relates: Eventually, the three converts gathered together in one place, and they said: Shammai’s impatience sought to drive us from the world; Hillel’s patience brought us beneath the wings of the Divine Presence.