“And I have given the Levites as a gift to Aaron and to his sons from among the children of Israel, to do the service of the children of Israel in the tabernacle of the congregation, and to make an atonement for the children of Israel: that there be no plague among the children of Israel, when the children of Israel come nigh unto the sanctuary.”
King James Version (KJV)
8:19 To do the service of Israel - To serve God in their stead, to do what otherwise they had been obliged to do in their own persons. To make an atonement - Not by offering sacrifices, which the priests alone might do, but by assisting the priests in that expiatory work, and by a diligent performance of all the parts of their office, whereby God was pleased both with them and with the people. That there be no plague - This is added as a reason why God appointed them to serve in the tabernacle, that they might guard it, and not suffer any of the people to come near it, or meddle with holy things, which if they did, it would certainly bring a plague upon them.