“I will give to you, and to your descendants after you, the land of your sojourning, the entire land of Canaan for an eternal holding, and I will be their God” (Genesis 17:8). “I will give to you, and to your descendants after you, the land of your sojourning” – Rabbi Yudan said five things:35The passage alludes to five covenants contingent one upon the other. If your descendants accept My Godliness upon themselves, I will be God and patron for them; if not, I will not be God and patron for them.
If your descendants enter the land, they will be able to accept My Godliness, but if not, they will not be able to accept it.36One who does not dwell in the land of Israel is lacking in his realization of God’s mastery)see Ketubot 110b). If your descendants fulfill the precept of circumcision, they will enter the land; but if not, they will not enter the land. If your descendants accept the Shabbat they will enter the land;37Shabbat, like circumcision, is referred to as “an eternal covenant for your generations” (Genesis 17:7, Exodus 31:16). but if not, they will not enter the land.
“God said to Abraham: And you, you shall observe My covenant, you, and your descendants after you, throughout their generations” (Genesis 17:9). Rabbi Berekhya and Rabbi Ḥelbo in the name of Rabbi Avun ben Rabbi Yosei: It is written: “This is the matter [hadavar] that Joshua circumcised” (Joshua 5:4) – Joshua made a statement [davar] to them and circumcised them. He said to them: ‘What do you think, that you will enter the land uncircumcised?
So the Holy One blessed be He said to Abraham our patriarch: “I will give to you and to your descendants after you, [the land of your sojourning],” with the provision that: “And you, you shall observe My covenant.”’ “And you, you shall observe My covenant” – Rabbi Huna and Rabbi Yoḥanan, Rabbi Huna said: “And you” – from here we learn that the circumciser must himself be circumcised. Rabbi Yoḥanan said: “You shall surely circumcise [himol yimol]” (Genesis 17:13) – from here38From the double expression himol yimol. we learn that the circumciser must himself be circumcised. It is taught: An uncircumcised Israelite may not be a circumciser; all the more so, an uncircumcised idolater.