9
The only responsibility the Levites have is to serve Aaron and his sons.
10
You shall appoint Aaron and his sons to carry out the duties of the priesthood; anyone else who tries to do so shall be put to death."
12
"The Levites are now to be mine. When I killed all the first-born of the Egyptians, I consecrated as my own the oldest son of each Israelite family and the first-born of every animal. Now, instead of having the first-born sons of Israel as my own, I have the Levites; they will belong to me. I am the Lord."