Numbers 3:16

12 “Behold, I have taken the Levites from among the children of Israel in place of every firstborn Israelite from the womb. The Levites belong to Me,

13 for all the firstborn are Mine. On the day I struck down every firstborn in the land of Egypt, I consecrated to Myself all the firstborn in Israel, both man and beast. They are Mine; I am the LORD.”

14 Then the LORD spoke to Moses in the Wilderness of Sinai, saying,

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

16 So Moses numbered them according to the word of the LORD, as he had been commanded.

17 These were the sons of Levi by name: Gershon, Kohath, and Merari.

18 These were the names of the sons of Gershon by their clans: Libni and Shimei.

19 The sons of Kohath by their clans were Amram, Izhar, Hebron, and Uzziel.

20 And the sons of Merari by their clans were Mahli and Mushi. These were the clans of the Levites, according to their families.

Read all of Numbers 3