1 Corinthians 9:13-14

don't you know, that they who prepare the sacrifices, do eat of the sacrifice in the temple? and they who wait at the altar, have their portion from the altar?

Galatians 6:6

Let him that is instructed in the word freely communicate his good things to him that teaches him.

Hebrews 7:5

'tis true they of the race of Levi, who assume the office of the priesthood, have a right by law to take tithes of the people, that is, of their brethren, though they all issued from Abraham:

Treasury of Scripture Knowledge

Summary

And, behold, I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve, even the service of the tabernacle of the congregation.

Bible References

Even the service

1 Corinthians 9:13
don't you know, that they who prepare the sacrifices, do eat of the sacrifice in the temple? and they who wait at the altar, have their portion from the altar?
Galatians 6:6
Let him that is instructed in the word freely communicate his good things to him that teaches him.