וַֽיִּצְבְּאוּ֙ עַל־מִדְיָ֔ן כַּאֲשֶׁ֛ר צִוָּ֥ה יְהוָ֖ה אֶת־מֹשֶׁ֑ה וַיַּֽהַרְג֖וּ כָּל־זָכָֽר׃
Y pelearon contra Madián, como SEÑOR lo mandó á Moisés, y mataron á todo varón.
Rabbeinu Bahya
ויהרגו כל זכר, “they killed every male,” i.e. the adults. The male children were part of the loot as per verse 9.