Deuteronomy 21:4 WEB

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;

⁴  and the elders of that city shall bring down the heifer to a valley with running water, which is neither plowed nor sown, and shall break the heifer's neck there in the valley.

⁵  The priests the sons of Levi shall come near; for them Yahweh your God has chosen to minister to him, and to bless in the name of Yahweh; and according to their word shall every controversy and every stroke be.

⁶  All the elders of that city, who are nearest to the slain man, shall wash their hands over the heifer whose neck was broken in the valley;