Seven days you shall make atonement for the altar and sanctify it. And the altar shall be most holy. Whatever touches the altar must be holy.
Exodus 29:37
Surrounding context
29:36 And you shall offer a bull every day as a sin offering for atonement. You shall cleanse the altar when you make atonement for it, and you shall anoint it to sanctify it.
29:37 Seven days you shall make atonement for the altar and sanctify it. And the altar shall be most holy. Whatever touches the altar must be holy.
29:38 "Now this is what you shall offer on the altar: two lambs of the first year, day by day continually.