Rabbi Eliezer (Kesubos 10b) stated that the korbonos brought on the mizbeiach, altar, accomplish four great things:
1) Maiziach: removed evil decrees
2) Mazin: nourished
3) Mechavaive: caused Israel to be beloved by Hashem
4) Mechapair: caused sins to be forgiven.
The mizbeiach which begins with Mem brings four benefits which start with the letter Mem. The Milah, circumcision, has the same properties. The Sefer Malach HaBris explains that when Tzipporah performed the Bris on Eliezer after Moshe almost died she exclaimed, “a husband of blood (damim) you (almost) were to me (See Shemos 4:25 and Soforno). Damim can be read as Daled Memim, four Mems! Thus Milah which takes the place of the mizbeiach brings four benefits of purity as well.