Numbers 3:15 WEB

¹³  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 Yahweh.'

¹⁴  Yahweh spoke to Moses in the wilderness of Sinai, saying,

¹⁵  'Number the children of Levi by their fathers' houses, by their families: every male from a month old and upward shall you number.'

¹⁶  Moses numbered them according to the word of Yahweh, as he was commanded.

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