Numbers 3:6
"Bring the tribe of Levi and present them to Aaron the priest to assist him.

Numbers 8:5
Again the LORD spoke to Moses, saying,

2 Chronicles 29:11
Now, my sons, do not be negligent, for the LORD has chosen you to stand before Him, to serve Him, to minister before Him, and to burn incense."

Isaiah 52:11
Depart, depart, go out from there! Touch no unclean thing; come out from it, purify yourselves, you who carry the vessels of the LORD.