28:15-30 The chief ornament of the high priest, was the breastplate, a rich piece of cloth, curiously worked. The name of each tribe was graven in a precious stone, fixed in the breastplate, to signify how precious, in God's sight, believers are, and how honourable. How small and poor soever the tribe was, it was as a precious stone in the breastplate of the high priest; thus are all the saints dear to Christ, however men esteem them. The high priest had the names of the tribes, both on his shoulders and on his breast, which reminds us of the power and the love with which our Lord Jesus pleads for those that are his. He not only bears them up in his arms with almighty strength, but he carries them in his bosom with tender affection. What comfort is this to us in all our addresses to God! The Urim and Thummim, by which the will of God was made known in doubtful cases, were put in this breastplate. Urim and Thummim signify light and integrity. There are many conjectures what these were; the most probable opinion seems to be, that they were the twelve precious stones in the high priest's breastplate. Now, Christ is our Oracle. By him God, in these last days, makes known himself and his mind to us, Heb 1:1,2; Joh 1:18. He is the true Light, the faithful Witness, the Truth itself, and from him we receive the Spirit of Truth, who leads into all truth.
30. thou shalt put in the breastplate of judgment the Urim and Thummim—The words signify "lights" and "perfections"; and nothing more is meant than the precious stones of the breastplate already described (compare Ex 39:8-21; Le 8:8). They received the name because the bearing of them qualified the high priest to consult the divine oracle on all public or national emergencies, by going into the holy place—standing close before the veil and putting his hand upon the Urim and Thummim, he conveyed a petition from the people and asked counsel of God, who, as the Sovereign of Israel, gave response from the midst of His glory. Little, however, is known about them. But it may be remarked that Egyptian judges wore on the breast of their official robes a representation of Justice, and the high priest in Israel long officiated also as a judge; so that some think the Urim and Thummim had a reference to his judicial functions.