Deuteronomy 21:2-8

2then your elders and your judges shall go out and measure the distance from the slain man to the surrounding cities.

3And it shall be that the elders of the city nearest to the slain man will take a heifer which has not been worked and which has not pulled with a yoke.

4The elders of that city shall bring the heifer down to a valley with flowing water, which is neither plowed nor sown, and they shall break the heifer’s neck there in the valley.

5Then the priests, the sons of Levi, shall come near, for the Lord your God has chosen them to minister to Him and to bless in the name of the Lord; by their word every controversy and every assault shall be settled.

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.