Numbers 3:13

10 `And Aaron and his sons thou dost appoint, and they have kept their priesthood, and the stranger who cometh near is put to death.`

11 And Jehovah speaketh unto Moses, saying,

12 `And I, lo, I have taken the Levites from the midst of the sons of Israel instead of every first-born opening a womb among the sons of Israel, and the Levites have been Mine;

13 for Mine [is] every first-born, in the day of My smiting every first-born in the land of Egypt I have sanctified to Myself every first-born in Israel, from man unto beast; Mine they are; I [am] Jehovah.`

14 And Jehovah speaketh unto Moses in the wilderness of Sinai, saying,

15 `Number the sons of Levi by the house of their fathers, by their families; every male from a son of a month and upward thou dost number them.`

16 And Moses numbereth them according to the command of Jehovah, as he hath been commanded.