Numbers 5:29

This is the law of jealousies— Grotius remarks justly, that "it is not to be wondered if God, among his own people, produced a miraculous effect for the detection of a crime most heinous, and very difficult to be proved. Indeed, history abounds with examples of the direful effects of jealousy, not only to private persons and families, but to whole states and kingdoms; the design, therefore, of this institution was to prevent these evils, by appointing a method whereby injured innocence might be cleared, and every shameful breach of conjugal fidelity brought to condign punishment. By this solemn and awful decision of Providence, jealous husbands were restrained from cruel outrages against their wives, and wives were preserved in their duty out of dread of this punishment." The Jews tell us, that this way of trial ceased towards the latter end of the second temple.