Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[220] If a murder be committed in any place, and he that did it be not found, nor is there any suspicion upon one as if he had hated the man, and so had killed him, let there be a very diligent inquiry made after the man, and rewards proposed to any one who will discover him; but if still no information can be procured, let the magistrates and senate of those cities that lie near the place in which the murder was committed, assemble together, and measure the distance from the place where the dead body lies; then let the magistrates of the nearest city thereto purchase a heifer, and bring it to a valley, and to a place therein where there is no land ploughed or trees planted, and let them cut the sinews of the heifer; then the priests and Levites, and the senate of that city, shall take water and wash their hands over the head of the heifer; and they shall openly declare that their hands are innocent of this murder, and that they have neither done it themselves, nor been assisting to any that did it. They shall also beseech God to be merciful to them, that no such horrid act may any more be done in that land.