Deuteronomy 21:1-9

If, in the land that Adonai your God is assigning you to possess, someone slain is found lying in the open, the identity of the slayer not being known, your elders and magistrates shall go out and measure the distances from the corpse to the nearby towns. The elders of the town nearest to the corpse shall then take a heifer which has never been worked, which has never pulled in a yoke; and the elders of that town shall bring the heifer down to an ever-flowing wadi, which is not tilled or sown. There, in the wadi, they shall break the heifer's neck. The priests, sons of Levi, shall come forward; for Adonai your God has chosen them to minister to God and to pronounce blessing in the name of Adonai, and every lawsuit and case of assault is subject to their ruling. Then all the elders of the town nearest to the corpse shall wash their hands over the heifer whose neck was broken in the wadi. And they shall make this declaration: "Our hands did not shed this blood, nor did our eyes see it done. Absolve, O Adonai, Your people Israel whom You redeemed, and do not let guilt for the blood of the innocent remain among Your people Israel." And they will be absolved of blood guilt. Thus you will remove from your midst guilt for the blood of the innocent, for you will be doing what is right in the sight of Adonai. [JPS translation edited for gender-neutrality]