After that, they may assist their brothers in fulfilling their duties at the Tent of Meeting, but they themselves are not to do the work. This is how you are to assign responsibilities to the Levites.”
We read before of the separating of the Levites from among the children of Israel when they were numbered, and the numbering of them by themselves (Num 3:6, Num 3:15), that they might be employed in the service of the tabernacle. Now here we have directions given for their solemn ordination (Num 8:6), and the performance of it, Num 8:20.
Commenting on Numbers 8:5-26
But shall minister with their brethren--in the performance of easier and higher duties, instructing and directing the young, or superintending important trusts. "They also serve who only wait" [MILTON]. Next: Numbers Chapter 9
But shall minister with their brethren in the tabernacle of the congregation, to keep the charge, and shall do no service. Thus shalt thou do unto the Levites touching their charge. (l) In singing Psalms, instructing, counselling and keeping the things in order.