אֵ֣לֶּה בְנֵֽי־לֵוִי֩ לְבֵ֨ית אֲבֹתֵיהֶ֜ם רָאשֵׁ֧י הָאָב֣וֹת לִפְקוּדֵיהֶ֗ם בְּמִסְפַּ֤ר שֵׁמוֹת֙ לְגֻלְגְּלֹתָ֔ם עֹשֵׂה֙ הַמְּלָאכָ֔ה לַעֲבֹדַ֖ת בֵּ֣ית יְהוָ֑ה מִבֶּ֛ן עֶשְׂרִ֥ים שָׁנָ֖ה וָמָֽעְלָה׃
These were the sons of Levi after their fathers’houses, even the heads of the fathers’houses, according to their muster, in the number of names by their polls, who did the work for the service of the house of the LORD, from twenty years old and upward.
Read midrashic interpretation of I Chronicles 23:24: and classical rabbinic exegesis.