Numbers 3:9-11

Complete Jewish Bible

⁹ Assign the L’vi’im to Aharon and his sons; their one responsibility in regard to the people of Isra’el is to serve him. ¹⁰ You are to appoint Aharon and his sons to carry out the duties of cohanim; anyone else who involves himself is to be put to death.”

¹¹ Adonai said to Moshe,