Midrasch zu Wajikra 4:30

4) "and all of its [remaining] blood he shall pour (at the base of the altar."). And above (Vayikra 4:25) it is written: "and its [remaining] blood he shall pour" — whence it is derived: a sin-offering whose blood was received in four vessels, from each of which he applied (blood at a different corner of the altar) — how do we know that they are all poured out at the foundation, (and not just the first, which effects atonement)? From: "and all of its blood he shall pour."

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).