Deuteronomy 21:1-7

If, in the land which the Lord your God is giving you, you come across the dead body of a man in the open country, and you have no idea who has put him to death: Then your responsible men and your judges are to come out, and give orders for the distance from the dead body to the towns round about it to be measured; And whichever town is nearest to the body, the responsible men of that town are to take from the herd a young cow which has never been used for work or put under the yoke; And they are to take the cow into a valley where there is flowing water, and which is not ploughed or planted, and there the neck of the cow is to be broken: Then the priests, the sons of Levi, are to come near; for they have been marked out by the Lord your God to be his servants and to give blessings in the name of the Lord; and by their decision every argument and every blow is to be judged: And all the responsible men of that town which is nearest to the dead man, washing their hands over the cow whose neck was broken in the valley, Will say, This death is not the work of our hands and our eyes have not seen it.