Rabbi said: Abraham did not delay aught with reference to all (things) which He commanded him, as it is said, "And he that is eight days old shall be circumcised" (Gen. 17:12); and when Isaac was born, (and when) he was eight days old (Abraham) brought him to be circumcised, as it is said, "And Abraham circumcised his son Isaac when he was eight days old" (Gen. 21:4). Hence thou mayest learn that everyone who brings his son for circumcision is as though (he were) a high priest bringing his meal offering and his drink offering upon the top of the altar.
Hence the sages said: A man is bound to make festivities and a banquet on that day when he has the merit of having his son circumcised, like Abraham our father, who circumcised his son, as it is said, "And Abraham circumcised || his son Isaac" (ibid.).