John Gill Commentary Numbers 18:6

"And I, behold, I have taken your brethren the Levites from among the children of Israel: to you they are a gift, given unto Jehovah, to do the service of the tent of meeting." — Numbers 18:6 (ASV)

And I, behold, I have taken your brethren the Levites, from
among the children of Israel (See Gill on Numbers 3:12); where the same is said, only they are here called the brethren of the priests for the reason given (Numbers 18:2); to you [they are] given [as] a gift for the Lord, to do the service of
the tabernacle of the congregation (See Gill on Numbers 3:7), (See Gill on Numbers 3:8), and (See Gill on Numbers 3:9).