Exodus 28:30

The Urim and the Thummim. These words mean, respectively, “light” and “perfection.” Though he does not specifically refer to the Urim and the Thummim by name, Josephus does speak of the “shining” of the stones on the breastplate of the high priest, which “shining,” he says, ceased two centuries previously, owing to the prevailing iniquity (Antiquities iii. 8. 9). Through these two stones God made known His will. A halo of light encircling the Urim was a token of the divine approval on matters brought before Him, and a cloud shadowing the Thummim was evidence of disapproval (Patriarchs and Prophets, p. 351). For instances of this see 1 Samuel 23:9-12; 28:6; 30:7, 8. The breastplate was to the garments of the high priest what the mercy seat was to the sanctuary itself. On both, God revealed His glory and made known His will (cf. Exodus 25:22; Psalm 80:1; Isaiah 37:16).