הלכה אויף בראשית 28:4

Circumcision was only commanded of Abraham and his descendents, as it says, “You and your descendents who will follow you throughout the generations” (Genesis 17:9). Ishmael’s descendents are excluded from this Commandment, as it says, “For through Isaac shall your descendents be called yours” (Genesis 21:12). Esau is excluded since Isaac said to Jacob, “and he shall give the blessing of Abraham to you and to your descendents” (Genesis 28:4). Since he, alone, was the descendent of Abraham who stood fast with his religion and his upright ways, it is his progeny who were commanded with circumcision.