Rebbi — Rabbi Yehuda HaNasi, the compiler of the Mishnah (the earliest code of rabbinic law) — declared that circumcision was so great that all of Moses' accumulated merits could not protect him when he was lax in performing it.
The story is one of the most mysterious episodes in the Torah. God had just commissioned Moses at the burning bush, telling him to go to Egypt and demand that Pharaoh release the Israelites. Moses obeyed. He took his wife Tzipporah and his sons and set out on the road. And then, at a lodging place along the way, "the angel sought to kill him" (Exodus 4:24).
The attack came without warning. An angel — sent by God Himself — tried to kill the very man God had just appointed as Israel's redeemer. The reason, according to rabbinic tradition, was that Moses had delayed the circumcision of one of his sons. For "a short time," as Rebbi put it, Moses had been lax in fulfilling this commandment, and that brief lapse nearly cost him his life.
Rebbi's teaching emphasizes the severity of the moment. This was Moses — the man who would part the Red Sea, ascend Mount Sinai, receive the Torah directly from God, and speak with the divine presence face to face. His merits were staggering, unmatched by any other human being in history. And yet those merits counted for nothing when weighed against the neglect of circumcision.
The covenant of circumcision, first commanded to Abraham (Genesis 17:10), was not one obligation among many. It was the foundational sign of the relationship between God and Israel — so fundamental that even the greatest prophet could not be exempted from its demands, not even for a moment, not even on a divinely commanded mission.