The Urim and Thummim were mounted on Aaron's ephod, and his priesthood represented the Lord in respect of Divine good and the effecting of salvation. The garments of priesthood or of holiness represented Divine truths coming from the Lord. The ephod represented Divine truth in its outermost form, that is, the Word in its literal sense, for this is Divine truth in its outermost form. Thus the twelve precious stones called Urim and Thummim, which bore the names of the twelve tribes of Israel, represented Divine truths coming from Divine good and all that goes with them. We read about these in the writings of Moses:

They are to make the ephod of [gold]*, violet and purple, with doubledyed scarlet and lawn interwoven. (Later) you are to make the breastpiece of judgment, of similar workmanship to the ephod, and you are to fill it with settings for stones. There are to be four rows of stones: ruby, topaz and emerald in the first row; chrysoprase, sapphire and diamond in the second row; turquoise, agate and amethyst in the third row; aquamarine, sardius and jasper in the fourth row. These stones are to answer to the names of the sons of Israel. The inscriptions as on a seal are to have each the name of one of the twelve tribes. And Aaron is to wear upon the breast-plate of judgment the Urim and Thummim; and let them be upon Aaron's heart, when he comes into the presence of Jehovah. Exod. 28:6, 15-21, 29, 30.

[2] The representations of Aaron's garments, his ephod, mantle, tunic, turban., and sash, have been explained in ARCANA CAELESTIA (published in London) in the commentary on this chapter. It was there shown that the ephod represented Divine truth in its outermost form; the precious stones the truths made pellucid by good; the twelve set out in four rows represented the whole from first to last; the twelve tribes the whole of the church. The breast-plate represented Divine truth coming from Divine good in the universal sense; the Urim and Thummim the splendour of Divine truth coming from Divine good in its outermost form. Urim is shining fire and Thummim splendour in the language of the angels, or wholeness in Hebrew. Again, replies were given by changes in the quality of light, accompanied by an unspoken perception, or by direct speech, and there is much besides. These explanations establish that these stones stood for truths coming from good in the outermost sense of the Word. For this is the only source by which replies are given from heaven, because that sense contains the Divine which proceeds in all its fulness.

* Apparently omitted by accident.