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.

5198. 'Seven cows were coming up' means the truths belonging to the natural. This is clear from the meaning of 'cows' as the truths belonging to the natural, dealt with below. The reason there were seven is that 'seven' means that which is holy, 395, 433, 716, and therefore this number contributes to any matter under consideration the idea of holiness, dealt with in 881. The matter under consideration here is likewise of a holy nature since it concerns a further rebirth of the natural through the joining of this to the celestial of the spiritual. As regards 'cows' or 'young cows' meaning the truths belonging to the natural, this becomes clear from the fact that 'bulls' and 'young bulls' mean forms of good belonging to the natural, 2180, 2566, 2781, 2830. For in the Word, when a male means good, its female means truth, and conversely when the male means truth its female means good, so that 'a cow' means some truth belonging to the natural, because 'a bull' means some form of good belonging to it.

[2] All beasts without exception that are mentioned in the Word mean affections, evil and useless beasts meaning evil affections, gentle and useful ones meaning good affections, see 45, 46, 142, 143, 246, 714, 715, 719, 776, 1823, 2179, 2180, 3218, 3519. The reason why they have such a meaning lies in the representations that occur in the world of spirits, for whenever a discussion about affections is taking place in heaven, beasts corresponding to affections of the kind under discussion are represented in the world of spirits, as I have also been allowed quite often to see. On several occasions I have wondered about the origin of that phenomenon, but have been led to perceive that the lives led by beasts are nothing else than affections; for they respond instinctively, devoid of reason, to their innate affections and are led by these to fulfill their specific functions. No other physical forms are suited to these affections devoid of reason than the kinds in which they are seen on earth. This explains why, when the discussion in heaven is about affections alone, the ultimate forms that those affections take in the world of spirits are the same in appearance as the physical forms of such beasts; for those affections cannot be clothed with any other forms than ones such as correspond to them. I have also seen beasts, the like of which do not appear anywhere at all in the natural world. They were the forms taken by affections that are not known and by affections that are mingled together.

[3] Here then is the reason why in the Word affections are meant by 'beasts', though which particular affections are meant cannot be seen from anywhere else than the internal sense. 'Bulls' means the good belonging to the natural, as may be seen in the paragraphs listed above; and as for the meaning of 'cows' as the truths belonging to the natural, this becomes clear from other places where they are referred to, such as Isaiah 11:7; Hosea 4:16; Amos 4:1, as well as from the reference in Numbers 19:2-10 to the water of separation by which they were to be made clean and which was prepared from the red cow burned to ashes outside the camp, with which cedar wood was mixed, hyssop, and twice-dyed scarlet. When the meaning of this procedure is disclosed with the help of the internal sense, it shows that 'the red cow', meaning unclean truth within the natural, is made clean by 'burning', and also by the kinds of things meant by 'cedar wood, hyssop, and twice-dyed scarlet'. The water prepared by that process represented the means of purification.