The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.

9905. 'And you shall put into the breastplate of judgement the Urim and Thummim' means the radiance of Divine Truth from the Lord in last and lowest things. This is clear from the meaning of 'the breastplate of judgement' as Divine Truth shining forth from the Lord's Divine Good, dealt with in 9857; and from the meaning of 'the Urim and Thummim' as the light and radiance from there. The reason why light and radiance are meant by 'the Urim and Thummim' is that through the stones in the breastplate varying radiations of the light of heaven were emitted, these being determined by the answers given through them. This also explains why they assumed different colours. For the Divine Truth emanating from the Lord's Divine Good manifests itself to the angels as light; it is the source of all the light of heaven. The colours from it, which are modifications of that light among the angels, are variations of intelligence and wisdom among them; for all wisdom and intelligence is a product of that Divine Truth or light. From this it may be recognized that radiations of that light in various colours are the medium through which Divine Truths coming as answers present themselves in the heavens. A similar function was served by the Urim and Thummim when God was asked something. But it should be remembered that whenever a radiance was seen in them the answer was declared at the same time by an audible voice. This declaration was made through angels, to whom what they declared had been revealed by the Lord through such a radiance; for as has been stated, this is how Divine Truths coming as answers present themselves in heaven.

[2] The light of heaven is Divine Truth emanating from the Lord's Divine Good, see 1053, 1521-1533, 1619-1632, 2776, 3094, 3138, 3167, 3190, 3195, 3222, 3223, 3337, 3339, 3341, 3636, 3643, 3862, 3993, 4060, 4180, 4302, 4408, 4414, 4415, 4419, 4527, 4598, 5400, 6032, 6313, 6315, 6608, 6907, 7174, 8644, 8707, 8861, 9399, 9407, 9570, 9571 (end).

Colours appear in heaven, being modifications of that light among the angels, and so variations of intelligence and wisdom among them, 3993, 4530, 4677, 4742, 4922, 9466, 9467, 9865.

[3] The meaning of the words 'Urim' and 'Thummim' also goes to show that all this is so; for 'Urim' means a shining fire, and 'Thummim' the radiance from it. A shining fire is the Divine Truth emanating from the Divine Good of the Lord's Divine Love, and the radiance is that Truth on last and lowest levels, thus in effects. It should be recognized however that 'Thummim' in the Hebrew language means wholeness; it is in the angelic language that it means radiance. The expression 'in the angelic language' is used because when angels talk to one another they are thinking of the very essence of some matter as perceived deep within themselves, thus they speak in terms of its essential nature. What they express flows from those insights into appropriate sounds audible to the angels alone. The appropriate sound for the radiance of Divine Truth is Thummim. This then is the source of the term. Angels have a similar understanding of the word thum, meaning that which is whole or wholeness, whenever someone reads it in the Hebrew language. This explains why in the internal sense of the Word 'that which is whole' is used to mean Divine Truth on the level of effects, which is a life led in keeping with Divine commandments, as is made clear in a large number of places in the Word, such as Joshua 24:14; Judges 9:16, 19; Psalms 25:21; 37:37; 84:11; 101:2; 119:1.

[4] This also explains why the Urim and Thummim are called the judgement of the children of Israel, as well as the breastplate of judgement, and also the judgement of the Urim; for 'judgement' means Divine Truth in doctrine and life, see above in 9857. From all this it may now become clear that by means of the Urim and Thummim, that is, by means of the radiance produced by the light of heaven, the breastplate revealed Divine Truths in the natural sphere, thus on last and lowest levels. A like radiance also presents itself in the minds of those who are guided by truths springing from good. This radiance declares to them, so to speak provides the answers, when with heartfelt desire they seek to know what is true and love it as that which is good. That this kind of radiance is the means by which Divine Truth from heaven is revealed in the natural man of those who are enlightened by the Word is something which the world has no idea of, because the world does not know of any light from heaven that shines in the human understanding. But I have been allowed to realize and actually see that all this is so.

[5] In addition it should be recognized that this radiance appears on last and lowest levels because all forms of light from the Divine reach right down to the furthest ends; and since they reach down that far they also shine in them and from them. This now explains why the breastplate was placed over the ephod and above the girdle of it; for the ephod represented Divine Truth on last and lowest levels, 9824, while its girdle represented a common bond that existed to hold all things in connection, 9828, 9837. This is why verse 28 of the present chapter says, And they shall tie the breastplate from its rings to the rings of the ephod, so that it is above the girdle of the ephod and the breastplate will not come away from upon the ephod. The reason why the names of the sons of Israel were in addition engraved [on the stones] was that the twelve tribes also represented all aspects of Divine Good and Truth in the heavens, consequently heaven and all the communities there, though that representation varied according to the order in which they are mentioned in the Word, see 3858, 3862, 3926, 3939, 4060, 4603, 6335, 6337, 6397, 6640, 7836, 7891, 7973, 7996, 7997.