Numbers 4:22 (ESV)
22 “Take a census of the sons of Gershon also, by their fathers’ houses and by their clans.
The phrase serves as brackets around the section that it is designed to mark off. This literary feature is not uncommon in the Bible and is associated with a literary device known as chiasm.
2 “Take a census of the sons of Kohath from among the sons of Levi, by their clans and their fathers’ houses,