Midrash Rabbah Beresheet on Abraham's Circumcision as an Offering

"Rabbi Levi opened: 'And a bull and a ram for a peace-offering (shelamim) to slaughter before the Lord, ... for today the Lord appears to you' (Leviticus 9:4).  Rabbi Levi said: Now if for this one who offered a bull and a ram for My sake, I will reveal Myself to him and bless him, then regarding Abraham, who circumcised himself for My sake, how much more so!  This is why immediately after the story of the circumcision it is written: 'The Lord appeared to him in the plans of Mamre' (Genesis 18:1) to indicate that God came to bless him in reward for having performed the mitzvah of circumcision."

-- Midrash Rabbah Beresheet, 48.5


Implicit in Rabbi Levi's midrash is the idea of Abraham's circumcision being analogous to the ritual sacrifices offered by the Kohanim in the Beit HaMikdash.