Why does the Torah record how many died in the plague?
Rosh: This teaches how much evil Zenus causes. This was Yechidi 1 , and 24,000 died due to it.
This connotes that this was the only Zenus. Verse 1 says that the Am was being Mezanah with Benos Mo'av! In verse 1, the Rosh said that from the days of Avraham, no Yisrael stumbled in Zenus. Perhaps Yechidi means the only episode of Zenus. Or, the plague was due to those who saw this lone brazen case of Zenus in public, and were not enraged. (PF)
Why is there an Esnachta in the verse, under "ba'Magefah?" The entire verse teaches only one matter! (An Esnachta always ends a matter, like a semicolon in English.)
R. Feivel Masmargan, cited in Divrei Eliyahu (Parshas Bo): Hashem had decreed that 24,000 die, but now was a time of Ratzon (He was not angry the entire time that Bil'am wanted to curse