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.

288. Since heaven's peace is a divine blessedness that profoundly affects the essential good within angels, it does not come to their open perception except through a heartfelt delight when they are involved in the good of their life, a pleasure when they hear something true that is in accord with their good, and a gaiety of mind when they perceive the union of the two. Still, it does flow into all the acts and thoughts of their life and makes itself known as joy, even in outward form.

[2] Peace varies in quality and quantity in the heavens, though, in proportion to the innocence of the people in any given location, because innocence and peace walk hand in hand. For as already noted, innocence is the source of everything good in heaven and peace is the source of all the joy of that good. We may conclude, then, that we can say much the same about the state of peace as has already been said about the state of innocence in the preceding chapter, since innocence and peace are united the way anything good and its delight are. Whatever is good is in fact sensed by its delight, and whatever is delightful is recognized by virtue of its goodness. This being the case, we can see that angels of the inmost or third heaven are in the third or inmost level of peace because they are in the third or inmost level of innocence, and that angels of the lower heavens are in lesser levels of peace because they are in lesser levels of innocence (see above, 280).

[3] If we look at little children, we can see that innocence and peace occur together in the same way that anything good and its delight do. Because they are in innocence, they are at peace as well; and because they are at peace, everything associated with them has a playful quality. However, their peace is an outward peace. Inner peace, like inner innocence, is found only in wisdom; and since it does dwell in wisdom, it is found in the union of the good and the true, since this is the origin of wisdom.

Heavenly or angelic peace occurs in us when we are attuned to wisdom because of the union of the good and the true and therefore see ourselves as contented in God. However, as long as we are living in this world, that peace lies hidden in our depths. Still, it is unveiled when we leave our bodies behind and enter heaven, because then those depths are opened.