"Urim and Thummim - objects that were placed on the vest of the high priest; used to determine God's will for the nation of Israel."
here is a definition from dictionary.com
objects, possibly made of metal or precious stones and inscribed with symbols, worn in the breastplate of the high priest and used, perhaps like lots, to determine God's response to a question answerable by “yes” or “no.”
An interesting subject indeed. There are more than a few opinions on the objects such as were the a part of the Priest's Breastplate or were they separate objects placed on the breastplate. Basically translating truth and light these objects (especially the Urim) was used to divine the will of God in a matter.
תּוּמִים (Thummim) is widely considered to be derived from the consonantal root תּמִם (t-m-m), meaning faultless, while אוּרִים (Urim) has traditionally been taken to derive from a root meaning lights; these derivations are reflected in the Neqqudot of the masoretic text. In consequence, Urim and Thummim has traditionally been translated as lights and perfections (by Theodotion, for example), or, by taking the phrase allegorically, as meaning revelation and truth, or doctrine and truth (it appears in this form in the Vulgate, in the writing of Jerome, and in the Hexapla). It should be understood that there does not exist a /θ/ sound in Hebrew, so "Thummim" is really pronounced /tumim/.
However, although at face value the words are plural, the context suggests they are pluralis intensivus - singular words which are pluralised to enhance their apparent majesty. The singular forms - ur and tumm - have been connected by some early scholars with the Babylonian terms urtu and tamitu, meaning oracle and command, respectively. Many scholars now believe that אוּרִים (Urim) simply derives from the Hebrew term אּרּרִים (Arrim), meaning curses, and thus that Urim and Thummim essentially means cursed or faultless, in reference to the deity's view of an accused - in other words Urim and Thummim were used to answer the question innocent or guilty.
A passage - 1 Samuel 14:41 - in the Books of Samuel is regarded by biblical scholars as key to understanding the Urim and Thummim; the passage describes an attempt to identify a sinner via divination, by repeatedly splitting the people into two groups and identifying which group contains the sinner. In the version of this passage in the masoretic text, it merely describes Saul and Jonathan being separated from the rest of the people, and lots being cast between them; the Septuagint version, however, states that Urim would indicate Saul and Jonathan, while Thummim would indicate the people. In the Septuagint, a previous verse uses a phrase which is usually translated as inquired of God, which is significant as the grammatical form of the Hebrew implies that the inquiry was performed by objects being manipulated; scholars view it as evident from these verses and versions that cleromancy was involved, and that Urim and Thummim were the names of the objects being cast.
The description of the clothing of the Jewish high priest in the Book of Exodus portrays the Urim and Thummim as being put into the sacred breastplate, worn by the high priest over the Ephod. Where the Bible elsewhere describes an Ephod being used for divination, scholars presume that it is referring to use of the Urim and Thummim in conjunction with the Ephod, as this seems to be intimately connected with it; similarly where non-prophets are portrayed as askingHaShem for guidance, and the advice isn't described as given by visions, scholars think that Urim and Thummim were the medium implied. In all but two cases (1 Samuel 10:22 and 2 Samuel 5:23), the question is one which is effectively answered by a simple yes or no; a number of scholars believe that the two exceptions to this pattern, which give more complex answers, were originally also just sequences of yes/no questions, but became corrupted by later editing.
There is no description of the form of the Urim and Thummim in the passage describing the high priest's vestments, and a number of scholars believe that the author of the passage, which textual scholars attribute to the priestly source, wasn't actually entirely aware of what they were either. Nevertheless, the passage does describe them as being put into the breastplate, which scholars think implies they were objects put into some sort of pouch within it, and then, while out of view, one (or one side, if the Urim and Thummim was a single object) was chosen by touch and withdrawn or thrown out; since the Urim and Thummim were put inside this pouch, they were presumably small and fairly flat, and were possibly tablets of wood or of bone. With the view of scholars that Urim essentially means guilty and Thummim essentially means innocent, this would imply that the purpose of the Urim and Thummim was an ordeal to confirm or deny suspected guilt; if the Urim was selected it meant guilt, while selection of the Thummim would mean innocence.
According to Islamic sources, there was a similar form of divination among the Arabs prior to the beginning of Islam. There, two arrow shafts (without heads or feathers), on one of which was written command and the other prohibition or similar, were kept in a container, and stored in the Kaaba at Mecca; whenever someone wished to know whether to get married, go on a journey, or to make some other similar decision, one of the Kaaba's guardians would randomly pull one of the arrow shafts out of the container, and the word written upon it was said to indicate the will of the god concerning the matter in question. Sometimes a third, blank, arrow shaft would be used, to represent the refusal of the deity to give an answer. This practice is called rhabdomancy, after the Greek roots rhabd- "rod" and -mancy ("divination").
According to classical rabbinical literature, in order for the Urim and Thummim to give an answer, it was first necessary for the individual to stand facing the fully dressed high priest, and vocalise the question briefly and in a simple way, though it wasn't necessary for it to be loud enough for anyone else to hear it. The Talmudic rabbis argued that Urim and Thummim were words written on the sacred breastplate; according to someone, the breastplate had to be activated by taking a parchment with the Tetragrammaton inscribed upon it, and inserting the parchment into a slot in the breastplate. Most of the Talmudic rabbis, and Josephus, following the belief that Urim meant lights, argued that divination by Urim and Thummim involved questions being answered by great rays of light shining out of certain jewels on the breastplate; each jewel was taken to represent different letters, and the sequence of lighting thus would spell out an answer (though there were 22 letters in the Hebrew alphabet, and only 12 jewels on the breastplate); two Talmudic rabbis, however, argued that the jewels themselves moved in a way that made them stand out from the rest, or even moved themselves into groups to form words.
1 Samuel 28:6 states that God refused to answer Saul by dreams, by Urim, or by prophets. Saul was a Benjamite; his 'yes' was Thummim. A priest is a Levite; his 'yes' is Urim. Six tribes were on one stone, and six tribes were on the other. Exo 28:9 And thou shalt take two onyx stones, and grave on them the names of the children of Israel: Exo 28:10 Six of their names on one stone, and the other six names of the rest on the other stone, according to their birth. Exo 28:11 With the work of an engraver in stone, like the engravings of a signet, shalt thou engrave the two stones with the names of the children of Israel: thou shalt make them to be set in settings of gold.
A passage of the Books of Samuel mentions three methods of divine communication - dreams, prophets, and the Urim and Thummim; the first two of these are also mentioned copiously in Assyrian and Babylonian literature, and such literature also mentions Tablets of Destiny, which are similar in some ways to the Urim and Thummim. The Tablets of Destiny had to rest on the breast of deities mediating between the other gods and mankind in order to function, while the Urim and Thummim had to rest within the breastplate of the priest mediating between HaShem and mankind. Marduk was said to have put his seal on the Tablets of Destiny, while the Israelite breastplate had a jewelled stone upon it for each of the Israelite tribes, which may derive from the same principle. Like the Urim and Thummim, the Tablets of Destiny came into use when the fate of king and nation was concerned. According to a minority of archaeologists, the Israelites emerged as a subculture from within Canaanite society, and not as an invading force from outside, and therefore it would be natural for them to have used similar religious practices to other Semitic nations, and scholars suspect that the concept of Urim and Thummim was originally derived from the Tablets of Destiny.
The first biblical reference to Urim and Thummim is the description in the Book of Exodus concerning the high priest's vestments; the chronologically earliest passage mentioning them, according to textual scholars, is in the Book of Hosea, where it is implied, by reference to the Ephod, that the Urim and Thummim were fundamental elements in the popular form of the Israelite religion, in the mid 8th century BC. Consulting the Urim and Thummim was said to be permitted for determining territorial boundaries, and was said to be required, in addition to permission from the king or a prophet, if there was an intention to expand Jerusalem or the Temple in Jerusalem; however, these rabbinical sources did question, or at least tried to justify, why Urim and Thummim would be required when a prophet was also present. The classical rabbinical writers argued that the Urim and Thummim were only permitted to be consulted by very prominent figures such as army generals, the most senior of court figures, and kings, and the only questions which could be raised were those which were asked for the benefit of the people as a whole.
Although Josephus argues that the Urim and Thummim continued to be used until the era of the Maccabees, Talmudic sources are unanimous in agreeing that the Urim and Thummim were lost much earlier, when Jerusalem was sacked by the Babylonians. In a passage from the part of the Book of Ezra which overlaps with the Book of Nehemiah, it is mentioned that individuals who were unable to prove, after the Babylonian captivity had ended, that they were descended from the priesthood before the captivity began, were required to wait until priests in possession of Urim and Thummim were discovered; this would appear to confirm the Talmudic view that the Urim and Thummim had by then been lost. Indeed, since the priestly source, which textual scholars date to a couple of centuries prior to the captivity, doesn't appear to know what the Urim and Thummim looked like, and there is no mention of the Urim and Thummim in the deuteronomic history beyond the death of David, biblical scholars suspect that use of them decayed some time before the Babylonian conquest, probably as a result of the growing influence at the time of prophets