Numbers 18:7-8

18:7 But you and your sons with you are responsible for your priestly duties, for everything at the altar and within the curtain. And you must serve. I give you the priesthood as a gift for service; but the unauthorized person who approaches must be put to death.”

The Portion of the Priests

18:8 The Lord spoke to Aaron, “See, I have given you the responsibility for my raised offerings; I have given all the holy things of the Israelites to you as your priestly portion and to your sons as a perpetual ordinance.

Deuteronomy 33:8-10

Blessing on Levi

33:8 Of Levi he said:

Your Thummim and Urim belong to your godly one,

whose authority you challenged at Massah,

and with whom you argued at the waters of Meribah.

33:9 He said to his father and mother, “I have not seen him,”

and he did not acknowledge his own brothers

or know his own children,

for they kept your word,

and guarded your covenant.

33:10 They will teach Jacob your ordinances

and Israel your law;

they will offer incense as a pleasant odor,

and a whole offering on your altar.