Deuteronomy 21:6-9
6 Then all the elders of the town nearest the body shall wash their hands over the heifer whose neck was broken in the valley,
7 and they shall declare: “Our hands did not shed this blood, nor did our eyes see it done.
8 Accept this atonement for your people Israel, whom you have redeemed, O Lord, and do not hold your people guilty of the blood of an innocent man.” And the bloodshed will be atoned for.
9 So you will purge from yourselves the guilt of shedding innocent blood, since you have done what is right in the eyes of the Lord.