1 Samuel 23:9

The ephod. By his own malicious act against the priests Saul had deprived himself of the benefits of the Urim and the Thummim, if indeed the Lord had communicated with him in this manner since his rejection (see chapter 28:6). No longer receiving divine communications, he quieted his accusing conscience by seeing, in every opening, a revelation of God to himself that was in harmony with the cravings of his diseased mind. By divine providence, and doubtless because of David’s consecration to do God’s will at all costs, the ephod, lost by Saul, found its way to David.

The Scriptures do not disclose the exact way in which the Urim and the Thummim gave the answers to inquiry. This silence has caused much speculation among the rabbis. The Babylonian Talmud states that the oracle was called Urim because it gave explanatory light to its utterances; it was called Thummim because its declarations were always complete. The tradition took these stones to be the ones on which the names of the 12 tribes were inscribed, and taught that the letters needed to spell out the reply were raised like the letters on a coin. The letters composing the names of the 12 tribes did not make up the letters of the entire Hebrew alphabet, but tradition added to these the names “Abraham,” “Isaac,” “Jacob,” and “Tribes of Jeshurun” (Treatise Yoma 73, a, b).

Josephus said: “God declared beforehand, by those twelve stones which the high priest bare on his breast, and which were inserted into his breastplate, when they should be victorious in battle; for so great a splendor shone forth from them before the army began to march, that all the people were sensible of God’s being present for their assistance” (Antiquities iii. 8. 9). However the Urim and the Thummim were not the 12 stones of the breastplate but 2 stones of great brilliance, one on each side of the breastplate. Approval was indicated by a light encircling the stone at the right and disapproval by a shadow on the stone at the left (see PP 351). The answers ascribed to the Urim and the Thummim were not always the equivalent of Yes or No (see Judges 1:2; 20:18; 1 Samuel 23:11, 12), but it is possible that the priest gave an answer in sentence form, in answer to a series of questions.