Numbers 8:19 in the King James Version
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.
Context
18 I have taken the Levites instead of all the firstborn among the children of Israel.
19 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 Tent of Meeting, and to make atonement for the children of Israel, so that there will be no plague among the children of Israel when the children of Israel come near to the sanctuary.”
20 Moses, and Aaron, and all the congregation of the children of Israel did so to the Levites. According to all that the LORD commanded Moses concerning the Levites, so the children of Israel did to them.