Deuteronomy 21:6

If one be found slain in the land which the LORD thy God giveth thee to possess it, lying in the field, and it be not known who hath slain him:

Then thy elders and thy judges shall come forth, and they shall measure unto the cities which are round about him that is slain:

And it shall be, that the city which is next unto the slain man, even the elders of that city shall take an heifer, which hath not been wrought with, and which hath not drawn in the yoke;

And the elders of that city shall bring down the heifer unto a rough valley, which is neither eared nor sown, and shall strike off the heifer's neck there in the valley: