Numbers 3:11-13; Numbers 3:45

11 Again the LORD spoke to Moses, saying,

12 "Now, behold, I have taken the Levites from among the sons of Israel instead of every firstborn, the first issue of the womb among the sons of Israel. So the Levites shall be Mine.

13 "For all the firstborn are Mine; on the day that I struck down all the firstborn in the land of Egypt, I sanctified to Myself all the firstborn in Israel, from man to beast. They shall be Mine; I am the LORD ."

45 "Take the Levites instead of all the firstborn among the sons of Israel and the cattle of the Levites. And the Levites shall be Mine; I am the LORD .