Numbers 3:12, 15, 45

And I, behold, I have taken the Levites from among the children of Israel instead of all the first-born that openeth the womb among the children of Israel; and the Levites shall be mine

Number the children of Levi by their fathers’ houses, by their families: every male from a month old and upward shalt thou number them.

Take the Levites instead of all the first-born among the children of Israel, and the cattle of the Levites instead of their cattle; and the Levites shall be mine: I am Jehovah.