창세기 17:21의 미드라쉬

These are the generations of Isaac, Abraham’s son: Abraham begot Isaac (Gen. 25:19). Scripture states elsewhere in allusion to this verse: The father of the righteous will greatly rejoice; and he that begetteth a wise child will have joy of him (Prov. 23:24). Concerning whom did Solomon make this statement? He said it about Isaac. When Isaac was born, the entire universe rejoiced; the heavens and the earth, the sun and the moon, the stars and the planets. Why did they rejoice? Because the world would not have survived had Isaac not been born, as it is said: If My covenant be not with day and night, if I have not appointed the ordinance of heaven and earth (Jer. 33:25). My covenant refers to Isaac, as it is said: I will establish My covenant with Isaac (Gen. 17:21).

THE TRIALS OF ABRAHAM (continued)
THE eighth trial (was as follows): "And when Abram was ninety-nine years old" (Gen. 17:1), the Holy One, blessed be He, said to him: Until now thou hast not been perfect before Me; but circumcise the flesh of thy foreskin, and "walk before me, and be thou perfect" (ibid.). Moreover, the foreskin is a reproach, as it is said, "For that is a reproach unto us" (Gen. 34:14), because the foreskin is more unclean than all unclean things, as it is said, "For henceforth there shall no more || come into thee the uncircumcised and the unclean" (Isa. 52:1). For the foreskin is a blemish above all blemishes. Circumcise the flesh of thy foreskin and be perfect.

Rabban Gamaliel said: Abraham sent and called for Shem, the son of Noah, and he circumcised the flesh of the foreskin of our father Abraham, and the flesh of the foreskin of Ishmael his son, as it is said, "In the selfsame day was Abraham circumcised, and Ishmael his son" (Gen. 17:26). "In the selfsame day" (means) in the might of the sun at midday. Not only that, but (it indicates) the tenth day of the month, the Day of Atonement. It is written in connection with the Day of Atonement, "Ye shall do no manner of work on that selfsame day, for it is a day of atonement" (Lev. 23:28); and in the present instance the text says, "In the selfsame day was Abraham circumcised" (Gen. 17:26). Know then that on the Day of Atonement Abraham our father was circumcised. Every year the Holy One, blessed be He, sees the blood of our father Abraham's circumcision, and He forgives all the sins of Israel, as it is said, "For on this day shall atonement be made for you, to cleanse you" (Lev. 16:30). In that place where Abraham was circumcised and his blood remained, there the altar was built, and therefore, "And all the blood thereof shall he pour out at the base of the altar" (Lev. 4:30). (It says also), "I said unto thee, In thy blood, live; yea, I said unto thee, In thy blood, live" (Ezek. 16:6).