Numbers 8:26
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.”
Berean Standard Bible
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.
but shall assist their brothers in the Tent of Meeting, to perform the duty, and shall perform no service. This is how you shall have the Levites do their duties.”