Numbers 4:17-19

New Revised Standard Version, Anglicised

¹⁷ Then the Lord spoke to Moses and Aaron, saying: ¹⁸ You must not let the tribe of the clans of the Kohathites be destroyed from among the Levites. ¹⁹ This is how you must deal with them in order that they may live and not die when they come near to the most holy things: Aaron and his sons shall go in and assign each to a particular task or burden.