Numbers 8:19-21

International Standard Version

¹⁹ I’ve set the descendants of Levi apart from the Israelis so that Aaron and his sons would work in service at the appointed place of meeting, making atonement on behalf of the Israelis so that there won’t be a plague among the Israelis whenever they approach the sanctuary.”

²⁰ So Moses and Aaron and the Israelis did this on behalf of the descendants of Levi. The Israelis did everything that the Lord commanded concerning the descendants of Levi. ²¹ The descendants of Levi therefore purified themselves, washed their clothes, and then Aaron presented them as wave offerings to the Lord. Aaron provided atonement for them to purify them.