Numbers 18:22-25

²²And henceforth the children of Israel shall not come nigh the tent of meeting, lest they bear sin, and die.

²³But the Levites alone shall do the service of the tent of meeting, and they shall bear their iniquity; it shall be a statute for ever throughout your generations, and among the children of Israel they shall have no inheritance.

²⁴For the tithe of the children of Israel, which they set apart as a gift unto the LORD, I have given to the Levites for an inheritance; therefore I have said unto them: Among the children of Israel they shall have no inheritance.'

²⁵And the LORD spoke unto Moses, saying: