Deuteronomy 21:1-3

“If a person who has been killed by someone is found lying in the open country in the land which the Lord your God is giving you to possess, and it is not known who struck him,

then your elders and your judges shall go out and measure the distance to the cities which are around the one who was killed.

And it shall be that the city which is nearest to the person killed, that is, that the elders of that city shall take a heifer of the herd that has not been worked and has not pulled in a yoke;