Deuteronomy 21:1-9

“If a slain person is found lying in the open country in the land which the LORD your God gives you to possess, and it is not known who has struck him, then your elders and your judges shall go out and measure the distance to the cities which are around the slain one. It shall be that the city which is nearest to the slain man, that is, the elders of that city, shall take a heifer of the herd, which has not been worked and which has not pulled in a yoke; and the elders of that city shall bring the heifer down to a valley with running water, which has not been plowed or sown, and shall break the heifer’s neck there in the valley. Then the priests, the sons of Levi, shall come near, for the LORD your God has chosen them to serve Him and to bless in the name of the LORD; and every dispute and every assault shall be settled by them. All the elders of that city which is nearest to the slain man shall wash their hands over the heifer whose neck was broken in the valley; and they shall answer and say, ‘Our hands did not shed this blood, nor did our eyes see it. Forgive Your people Israel whom You have redeemed, O LORD, and do not place the guilt of innocent blood in the midst of Your people Israel.’ And the bloodguiltiness shall be forgiven them. So you shall remove the guilt of innocent blood from your midst, when you do what is right in the eyes of the LORD.