Num 3:15

פְּקֹד֙ אֶת־בְּנֵ֣י לֵוִ֔י לְבֵ֥ית אֲבֹתָ֖ם לְמִשְׁפְּחֹתָ֑ם כָּל־זָכָ֛ר מִבֶּן־חֹ֥דֶשׁ וָמַ֖עְלָה תִּפְקְדֵֽם׃

“Number the Levites by their families and clans. You are to count every male a month old or more.”