Deuteronomy 21:1 WEB

¹  If one be found slain in the land which Yahweh your God gives you to possess it, lying in the field, and it isn't known who has struck him;

²  then your elders and your judges shall come forth, and they shall measure to the cities which are round about him who is slain:

³  and it shall be, that the city which is nearest to the slain man, even the elders of that city shall take a heifer of the herd, which hasn't been worked with, and which has not drawn in the yoke;