Deuteronomy 21:2-4

2Your leaders and your judges must then go to the field. They must measure how far the place is from the nearest towns.

3Then the leaders from the town that is nearest to the body must take a young cow that has never done work on a farm.

4They must lead the cow down to a valley where no one has ploughed the ground or planted seed. There must be a stream of water in the valley. There they must break the cow's neck.