Garments for the Priesthood and the Urim and Thummim
As Moses was the civil leader of the nation of Israel, the priesthood would be perpetuated through Aaron's lineage. The service of the Levites in general is not yet here established - as it is not implemented until after Israel's rebellion with the golden calf, which we'll soon read about. Consider once again the attention that is given to the wondrous and planned detail that God laid out for the adorning of the priesthood. Worshiping God is not a matter that is to be taken casually. When we come before God today, these principles still exist. Since God calls His Church a holy and royal priesthood (1 Peter 2:5 1 Peter 2:5You also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ.
American King James Version×, 9), our dress and grooming at worship services should, to the best of our ability, be of the highest standard.
Everything God does is filled with purpose. In this case, He sent His Spirit to guide the artisans in fashioning the priestly garments. The onyx stones engraved with the names of the tribes of Israel and the breastplate with their names symbolized the priest's intercessory work of representing the people before God. They were to be over his heart to impress upon him his responsibility. And over his forehead, representing the thoughts of the mind, was the engraving denoting devotedness to God. The bells on the garment "would tinkle as the priest moved about within the sacred places. This sound would assure those outside that the priest was interceding on their behalf" (Nelson Study Bible, note on verses 33-35).
Note the mention in verse 30 of "the Urim and the Thummim"-literally, in Hebrew, "the lights and the perfections." The Greek Septuagint renders this "revelation and truth." Indeed, as light often represents the knowledge of God in Scripture, perhaps the Hebrew wording denoted perfect knowledge of His will-discerned through this device, which seemed to constitute a plurality. Actually, we don't know for sure exactly what the Urim and Thummim was except for the testimony of the first-century Jewish historian Flavius Josephus, who, in relating the details of the ephod (Antiquities of the Jews, Book 3, chap. 7, sec. 5), refers to the breastplate as the "oracle" (Greek logion or "words") - as it evidently communicated a message from God. He goes on to imply that the Urim and Thummim was the breastplate stones shining in concert with the onyx (or sardonyx) stones on the shoulders, which held up the ephod on which the breastplate was affixed:
"For as to those stones which we told you before, the high priest bare on his shoulders, which were sardonyxes... the one of them shined out when God was present at their sacrifices; I mean that which was in the nature of a button on his right shoulder, bright rays darting out thence, and being seen even by those that were most remote; which splendor yet was not before natural to the stone. This has appeared a wonderful thing to such as have not so far indulged themselves in philosophy, as to despise Divine Revelation. Yet will I mention what is still more wonderful than this: for 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" (chap. 8, sec. 9).
God used this same device to impart more specific information as well. David consulted the Urim and Thummim concerning whether King Saul would come down to the city of Keilah and destroy it lest the residents betray David into his hands (1 Samuel 23:9-12 1 Samuel 23:9-12  And David knew that Saul secretly practiced mischief against him; and he said to Abiathar the priest, Bring here the ephod.
 Then said David, O LORD God of Israel, your servant has certainly heard that Saul seeks to come to Keilah, to destroy the city for my sake.
 Will the men of Keilah deliver me up into his hand? will Saul come down, as your servant has heard? O LORD God of Israel, I beseech you, tell your servant. And the LORD said, He will come down.
 Then said David, Will the men of Keilah deliver me and my men into the hand of Saul? And the LORD said, They will deliver you up.
American King James Version×). The answer? "He will come down" (verse 11). Exactly how this decision was communicated, we don't know. Perhaps they shone a certain way to indicate yes and no. Whatever happened, it should be pointed out that the Urim and Thummim was not in itself "magical." It was clear that God, who had Himself ordained this manner of contact - probably to demonstrate the importance of His nation approaching Him through His priesthood - was the one communicating. And it was clearly He who caused any supernatural emanations such as those described.