Numbers 3:12-13

“And I, behold, have taken the Levites from the midst of the sons of Israel instead of every firstborn opening a womb among the sons of Israel, and the Levites have been Mine; for every firstborn [is] Mine, in the day of My striking every firstborn in the land of Egypt I have sanctified to Myself every firstborn in Israel, from man to beast; they are Mine; I [am] YHWH.”