Jehovah God made circumcision mandatory for Abraham in 1919 B.C.E., a year before Isaac’s birth. God said: “This is my covenant that you men will keep . . . Every male of yours must get circumcised.” Every male in Abraham’s household of both his descendants and dependents was included, and so Abraham, his 13-year-old son Ishmael, and all his slaves took upon themselves this “sign of the covenant.” New slaves brought in also had to be circumcised. From then on, any male of the household, slave or free, was to be circumcised the eighth day after birth. Disregard for this divine requirement was punishable by death.​—Ge 17:1, 9-14, 23-27.

Others cite Herodotus as authority for their claim that Abraham simply borrowed the custom from the Egyptians. Answering these latter claims, W. M. Thomson says: “As to the testimony of Herodotus, who came into Egypt fifteen centuries after, and, with great learning and research, often writes a good deal of nonsense, I refuse utterly to put it in the same category with that of Moses. The great founder of the Jewish commonwealth​—the greatest lawgiver on record—​born and bred in Egypt, states the facts in relation to the introduction of circumcision among his people. A mere traveller and historian​—a foreigner and a Greek—​comes along very much later, and makes statements which are partly true, partly erroneous, as Josephus shows in his answer to Apion; and then sceptical authors, more than twenty centuries later than Herodotus, bring up his imperfect statements, and, twisting and expanding them, attempt to prove that Abraham did not receive circumcision from God (as Moses plainly says he did), but from the Egyptians! Not with such weapons can the veracity of Moses be successfully assailed.”​—The Land and the Book, revised by J. Grande, 1910, p. 593.

Abraham’s descendants through Isaac and Jacob faithfully kept the covenant of circumcision. “Abraham proceeded to circumcise Isaac his son when eight days old, just as God had commanded him.” (Ge 21:4; Ac 7:8; Ro 4:9-12) The great-grandsons of Abraham told Shechem and his fellow townsmen: “We cannot possibly . . . give our sister [Dinah] to a man who has a foreskin . . . Only on this condition can we give consent to you, that you become like us, by every male of yours getting circumcised.” (Ge 34:13-24) Apparently because Moses neglected to circumcise his son, he incurred God’s wrath until his wife Zipporah did it for him.​—Ex 4:24-26; see ZIPPORAH.