And the second row shall be an emerald, a sapphire, and a diamond.

Matthew Henry's Concise Commentary

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.