Numbers 8:15 MSG

[15] “After you have purified the Levites and presented them as a Wave-Offering to God, they can go to work in the Tent of Meeting. The Levites have been selected out of the People of Israel for my exclusive use; they function in place of every firstborn male born to an Israelite woman. Every firstborn male in Israel, animal or human, is set apart for my use. When I struck down all the firstborn of Egypt, I consecrated them for my holy uses. But now I take the Levites as stand-ins in place of every firstborn son in Israel, selected out of the People of Israel, and I have given the Levites to Aaron and his sons to do all the work involved in the Tent of Meeting on behalf of all the People of Israel and to make atonement for them so that nothing bad will happen to them when they approach the Sanctuary.”