Num Numbers, chapter Book of Numbers, chapter 3
And YHWH speaks to Moses, saying, “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; Exo 29:24; Num 8:16for 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.” Exo 13:2; Exo 22:29; Exo 34:19; Lev 27:26; Num 8:17; Luk 2:23