Numbers 25:14

ושם איש ישראל וגו׳ AND THE NAME OF THE ISRAELITE [WHO WAS SMITTEN] — Wherever it gives the genealogy of a good man in praise of him, it gives the genealogy of a bad man mentioned in the same story to disparage him (Midrash Tanchuma, Pinchas 2). נשיא בית אב לשמעני A PRINCE OF A FATHER’S HOUSE AMONGST THE SIMEONITES — of one of the five 'father’s houses' which were of the tribe of Simeon. — Another explanation: This is stated to tell the praiseworthiness of Phineas: that although this man was a prince he did not refrain from showing his zeal against the profanation of the Divine Name — on this account Scripture tells you who it was (a prince!) that was smitten by him.

וְשֵׁם֩ אִ֨ישׁ יִשְׂרָאֵ֜ל הַמֻּכֶּ֗ה אֲשֶׁ֤ר הֻכָּה֙ אֶת־הַמִּדְיָנִ֔ית זִמְרִ֖י בֶּן־סָל֑וּא נְשִׂ֥יא בֵֽית־אָ֖ב לַשִּׁמְעֹנִֽי׃

Now the name of the man of Yisra᾽el that was slain, that was slain with the Midyanite woman, was Zimri, the son of Salu, a prince of a father’s house among the Shim῾oni.