Numbers 3:9-10

9Give the Levites to Aaron and his sons; they are the Israelites who are to be given wholly to him. Most manuscripts of the Masoretic Text; some manuscripts of the Masoretic Text, Samaritan Pentateuch and Septuagint (see also 8:16) to me

10Appoint Aaron and his sons to serve as priests; anyone else who approaches the sanctuary is to be put to death.”