Numbers 3:16

for all the firstborn are mine. On the day that I struck down all the firstborn in the land of Egypt I made holy to me all the firstborn in Israel, both man and animal. They shall be mine. I am the LORD.”

The LORD spoke to Moses in the wilderness of Sinai, saying,

“Count the children of Levi by their fathers’ houses, by their families. You shall count every male from a month old and upward.”

These were the sons of Levi by their names: Gershon, Kohath, and Merari.

These are the names of the sons of Gershon by their families: Libni and Shimei.

The sons of Kohath by their families: Amram, Izhar, Hebron, and Uzziel.