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.

1198. 'From whom they came forth' means that cognitions, as these exist with them, are facts. This is clear from what has been stated. These are not said to have been 'begotten' by those who belonged to Egypt but to have 'gone forth', for they are not such as use natural and factual knowledge to reason about spiritual and celestial things and in so doing fabricate for themselves doctrinal teachings, as do those described before. Instead they learn cognitions of faith from another source, but have no other end in view to knowing and retaining these in the memory than they have with other things in which they have no interest beyond merely knowing them, and only then for the reason that by so knowing they may be promoted to positions of importance, and for other like reasons. So different is knowledge of cognitions of faith from knowledge of natural things that the two have scarcely anything in common. This explains why they are not said to have been 'bore' but to have 'gone forth' from them. Such being the character of 'Philistines' they inevitably pervert cognitions of faith by means of reasonings from them, and as a consequence fabricate false doctrines for themselves. They belong therefore among those who are barely able to be regenerated and to receive charity, both because they are uncircumcised at heart and because the false assumptions and consequently the life of their understanding hinder and prevent.