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.

2048. That 'he who is born in the houses means celestial people, and 'he who is the purchase of silver' spiritual people, and so those who are inside the Church, is clear from the meaning of 'him born in the house' as those inside the house. In the Word 'a house' means that which is celestial because this is inmost. Consequently 'the house of God' means in the universal sense the Lord's kingdom, in a less universal sense the Church, and in a particular sense the individual himself in whom the Lord's kingdom or Church exists. When a person is called 'a house' it means the celestial side of faith with him, but when he is called 'a temple' it means the truth of faith with him. So 'he who is born in the house' here means celestial people. That 'the purchase of silver' or one bought with silver means spiritual people however is clear from the meaning of 'silver' as truth, and so the spiritual side of faith, dealt with in Volume One, in 1551.

[2] The expression celestial is used of those who are governed by love to the Lord, and because the Most Ancient Church which existed before the Flood was governed by that love it was a celestial Church. The expression spiritual is used of those who are governed by love towards the neighbour and so by the truth of faith. This was the character of the Ancient Church that existed after the Flood. The difference between celestial people and spiritual has been dealt with many times in Volume One. Anyone may see that there are heavenly arcana here, that is to say, in the requirement to circumcise those born in the house and those bought with silver, also sons who were foreigners, and in the fact that those persons are mentioned repeatedly, for example, in verses 13, 23, 27, that follow. These arcana are not apparent however except from the internal sense, that is to say, that those born in the house and those bought with silver mean celestial people and spiritual, and so those inside the Church - while 'the son who is a foreigner and not of your seed' means those outside the Church.