Deuteronomy 21:6-9

6And all the elders of that city nearest to the slain man shall wash their hands over the heifer whose neck was broken in the valley.

7Then they shall answer and say, ‘Our hands have not shed this blood, nor have our eyes seen it.

8Provide atonement, O Lord, for Your people Israel, whom You have redeemed, and do not lay innocent blood to the charge of Your people Israel.’ And atonement shall be provided on their behalf for the blood.

9So you shall put away the guilt of innocent blood from among you when you do what is right in the sight of the Lord.