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.

5033. 'Saying, This is what your slave did to me' means corroboration. This becomes clear from his firm belief that his wife had spoken the truth, and that as a result her accusation, so far as he was concerned, was corroborated. The wife who convinced him means unspiritual natural truth, though at this point falsity is meant; for unspiritual natural good easily allows itself to be convinced by falsity, see immediately above in 5032. It is Well known that falsities can be corroborated to look exactly like truths. This is evident from all heresies and from every aspect of any heresy. Though they are falsities, corroborations of them nevertheless cause people who adhere to a heresy to see them as truths. The same point is evident in people who are not religious. These people in their thinking set themselves firmly against things of the Church, so firmly that they see as the truth the idea that the Church exists merely to keep the common people down. They also see as the truth the idea that natural forces are the be-all and end-all and that the Divine is so remote as to be virtually nothing at all, as well as the idea that in death the human being is no different from any animal. People with whom unspiritual natural good resides allow themselves, more easily than others, to be persuaded and convinced of these and similar ideas, for they have no mirror so to speak within themselves, only one outside themselves which makes illusions look like realities.