Deuteronomy 21:2-4

Revised Standard Version

² then your elders and your judges shall come forth, and they shall measure the distance to the cities which are around him that is slain; ³ and the elders of the city which is nearest to the slain man shall take a heifer which has never been worked and which has not pulled in the yoke. ⁴ And the elders of that city shall bring the heifer down to a valley with running water, which is neither plowed nor sown, and shall break the heifer’s neck there in the valley.