וּפְקוּדֵ֕י מִשְׁפְּחֹ֖ת בְּנֵ֣י מְרָרִ֑י לְמִשְׁפְּחֹתָ֖ם לְבֵ֥ית אֲבֹתָֽם׃
And those that were numbered of the families of the sons of Merari, by their families, by their fathers’houses,
Read midrashic interpretation of Numbers 4:42: and classical rabbinic exegesis.