And you shall put in the breastplate of judgment the Urim and the Thummim; and they shall be on Aaron's heart…
We lean to the opinion that the precious stones constituted the Urim and Thummim, but not by reason of any supernatural illumination of the letters, and that the stones rendered the breastplate the ornament or badge which qualified the high priest for making inquiries of Jehovah: "They shall be upon Aaron's heart when he goeth in before the Lord." The precious stones may have received the collective name of Urim and Thummim:
1. On their own account. Of all earthly objects, these precious stones are the most lustrous, and emit light of themselves. Like the stars they shine in the darkest night, and for that reason they have been called the "stars of earth." Are they not, then, well called lights? Thummim signifies perfection. The stones, from their brilliancy, purity, and uncommon beauty, are perhaps the most striking emblems which earthly objects furnish of truth or perfection, and are therefore not inappropriately named "Thummim."
2. On account of their being the badge or ornament which it was necessary for the high priest to wear when he consulted Jehovah. The object of the high priest was to get light on some dark subject, or to arrive at the truth on some matter he could not discover otherwise, or to give a righteous decision in cases in which his knowledge or wisdom was deficient, and such as would accord with innocence and justice. For these reasons the gems seem to be appropriately called "Urim and Thummim."
3. On account of their representing the children of Israel. The names of all the tribes being on the stones — one name on each — the Israelites might see in these stones an emblem of what it was designed they should become, before they were meet for being worshippers in the heavenly temple; and the high priest might be reminded by them that his mission was to bring the pious Israelite into that state of perfection. Like these gems, man by nature is of the earth earthy. Both have their origin in mother earth. Yet both, when polished, may shine like the stars of the firmament,
Parallel VersesKJV: And thou shalt put in the breastplate of judgment the Urim and the Thummim; and they shall be upon Aaron's heart, when he goeth in before the LORD: and Aaron shall bear the judgment of the children of Israel upon his heart before the LORD continually.
WEB: You shall put in the breastplate of judgment the Urim and the Thummim; and they shall be on Aaron's heart, when he goes in before Yahweh: and Aaron shall bear the judgment of the children of Israel on his heart before Yahweh continually.