Rashi on Numbers 25:6/רש"י על במדבר כ״ה:ו׳

1והנה איש וגו׳ AND BEHOLD, ONE [OF THE CHILDREN OF ISRAEL CAME] The tribe of Simeon gathered to Zimri who was their prince, saying to him. “We are sentenced to death and you remain quiet!?”, — as it is related in the chapter beginning אלו הן הנשרפין (Sanhedrin 82a).

2את המדינית THE MIDIANITISH WOMAN — Kozbi the daughter of Zur.

3לעיני משה BEFORE THE EYES OF MOSES — They said to him: “Moses, is this Midianite woman forbidden or permissible as a wife. If you say she is forbidden, then who made Jethro’s daughter, a Midianite woman, permissible to you, etc.” as is related there (Sanhedrin 82a).

4והמה בכים AND THEY WERE WEEPING — the law (decision on this matter) escaped him and therefore they all burst out into weeping (Sanhedrin 82a). — In the case of the golden calf Moses successfully resisted six hundred thousand men, as it is said, (Exodus 32:20) “And he ground it to powder [and he made the children of Israel drink of it]”, and here his hands were weak (he did not know what to do)?! But this was intentionally caused by God in order that Phineas might come and receive that which was meant for him (Midrash Tanchuma, Balak 20).