Urim and Thummim (אוּרִים, urim;, תֻּמִים, tumim). Objects kept in the breastpiece of the High Priest and used to discern the will of God.

The Urim and Thummim are mentioned in the Old Testament but never described, so their exact nature is unclear. Descriptions of Aaron’s vestments place the Urim and Thummim inside the “breastpiece of judgment” which Aaron wears over the ephod, so they must have been fairly small (Exod 28:30; Lev 8:8). They were likely a pair of objects, but since the words Urim and Thummim are both plural in form, it is possible that there were more than two objects.

Other passages indicate that the High Priest was to use the Urim and Thummim to discern the will of God (Num 27:21; 1 Sam 28:6; Ezra 2:63). None of these passages describe how they were to be used for this purpose, but it is often taken to involve some form of casting lots, which would qualify this as a form of divination. Some speculations include the following (Milgrom, Leviticus 1–16, 509–12):

1. They may have been a pair of stones used for casting lots, one of which would indicate “yes” and the other “no.”

2. They may have been an item for each letter of the alphabet. The name אוּרִים (urim) begins with aleph, the first letter of the Hebrew alphabet, while the name תֻּמִים (tumim) begins with tav, the last letter of the alphabet; the names of these endpoints may stand for the whole alphabet. Three letters chosen by lot could then form the root of a Hebrew word which would indicate the answer to the question.

3. They may have been two die-like objects, each with some sides marked with aleph for Urim and some sides marked with tav for Thummim; if the lots were cast such that both came up with the same mark, it would indicate a “yes” or “no” answer, while if the two came up with different marks, the result was inconclusive.