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.

3832. 'And made a feast' means the introduction. This is clear from the meaning of 'a feast' as making one's own and being joined to, dealt with in 3596. Here it is the introduction, for this precedes the joining together, and is a pledge and witness to it. The feasts which were held in early times by people among whom meaningful signs and representatives existed meant nothing else than the introduction into the mutual love which is the essence of charity. Wedding feasts meant the introduction into conjugial love, and sacred feasts the introduction into spiritual and celestial love, the reason being that 'feasting' or eating and drinking meant making one's own and becoming joined to, as shown in 3596.

[2] This being the meaning of 'feasts' the Lord also spoke in the same vein,

Many will come from the east and from the west and will recline with Abraham, Isaac, and Jacob in the kingdom of heaven. Matthew 8:11.

And elsewhere He said to the disciples,

That you may eat and drink at My table in My kingdom. Luke 22:30.

And when He instituted the Holy Supper He said,

I tell you that I shall not drink from now on of this fruit of the vine until that day when I drink it new with you in My Father's kingdom. Matthew 26:29.

Anyone may see that 'reclining', 'eating', and 'drinking' in the Lord's kingdom do not mean reclining, eating, and drinking, but the kind of thing that exists in that kingdom; that is to say, these experiences are used to mean making the good of love and the truth of faith one's own, and so to mean that which is called spiritual food and celestial food. The quotations given above also show plainly that there is an internal sense within words spoken by the Lord, and that without an understanding of that sense one cannot know what is meant by reclining with Abraham, Isaac, and Jacob, by eating and drinking at the Lord's table in His kingdom, and by drinking of the fruit of the vine with them in the Father's kingdom. Nor indeed can one know what is meant by eating bread and drinking wine in the Holy Supper.