Discovery BoxExodus 28:30 
Context28:30 “You are to put the Urim and the Thummim 1 into the breastpiece of decision; and they are to be over Aaron’s heart when he goes in before the Lord. Aaron is to bear the decisions 2 of the Israelites over his heart before the Lord continually.
Exodus 28:35
Context28:35 The robe 3 is to be on Aaron as he ministers, 4 and his sound will be heard 5 when he enters the Holy Place before the Lord and when he leaves, so that he does not die.
1 sn The Urim and the Thummim were two objects intended for determining the divine will. There is no clear evidence of their size or shape or the material of which they were made, but they seem to have been familiar items to Moses and the people. The best example of their use comes from 1 Sam 14:36-42. Some have suggested from the etymologies that they were light and dark objects respectively, perhaps stones or sticks or some other object. They seem to have fallen out of use after the Davidic period when the prophetic oracles became popular. It may be that the title “breastpiece of judgment” indicates that these objects were used for making “decisions” (J. P. Hyatt, Exodus [NCBC], 283-84). U. Cassuto has the most thorough treatment of the subject (Exodus, 378-82); he lists several very clear rules for their uses gathered from their instances in the Bible, including that they were a form of sacred lot, that priests or leaders of the people only could use them, and that they were used for discovering the divine will in areas that were beyond human knowledge.
2 tn Or “judgment” (KJV, ASV, NASB, NRSV). The term is מִשְׁפָּט (mishpat), the same word that describes the breastpiece that held the two objects. Here it is translated “decisions” since the Urim and Thummim contained in the breastpiece represented the means by which the
3 tn Heb “it”; the referent (the robe) has been specified in the translation for clarity.
4 tn The form is a Piel infinitive construct with the lamed (ל) preposition: “to minister” or “to serve.” It may be taken epexegetically here, “while serving,” although S. R. Driver takes it as a purpose, “in order that he may minister” (Exodus, 308). The point then would be that he dare not enter into the Holy Place without wearing it.
5 sn God would hear the bells and be reminded that this priest was in his presence representing the nation and that the priest had followed the rules of the sanctuary by wearing the appropriate robes with their attachments.
