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.

3720. 'This is nothing other than the house of God' means the Lord's kingdom as it exists in the ultimate degree of order. This is clear from the meaning of 'the house of God'. In the Word 'the house of God' is referred to in many places, and in the external sense, that is, literally, it means a building where holy worship takes place. But in the internal sense it means the Church, in the more universal sense it means heaven, and in the most universal the Lord's kingdom. In the highest sense however it means the Lord Himself as regards the Divine Human. But in the Word sometimes the expression 'House of God' is used and sometimes 'Temple'. The two are similar in meaning, the difference being that the expression 'House of God' is used when the subject is good but 'temple' when the subject is truth. From this it is evident that 'the House of God' means the Lord's celestial Church, and in the more universal sense the heaven of celestial angels, in the most universal the Lord's celestial kingdom, and in the highest sense the Lord as regards Divine Good; whereas 'the Temple' means the Lord's spiritual Church, and in the more universal sense the heaven of spiritual angels, in the most universal the Lord's spiritual kingdom, and in the highest the Lord as regards Divine Truth, see 2048. The reason why 'the House of God' means that which is celestial and the dwelling-place of good, while 'the Temple' means that which is spiritual and the dwelling-place of truth, is that 'a house' in the Word means good, see 710, 2233, 2559, 3128, 3652, and among the most ancient people used to be built of pieces of wood for the reason that 'wood' meant good, 643, 1110, 2784, 2812, whereas 'the Temple' means truth because it was built of stones - 'stones' meaning truths, see 643, 1296, 1298.

[2] These meanings that 'pieces of wood' and 'stones' possess are clear not only from the Word where they are mentioned but also from representatives in the next life. For people who assume that merit lies in good works seem to themselves to be cutting wood, and those who assume that it lies in truths, that is to say, people who have believed that they knew more truths than anybody else and yet have lived wickedly, seem to themselves to be breaking up stones. I have often seen such people wood-cutting or stone-breaking, from which the meaning of 'wood' and of 'stone' was made clear to me - that good is meant by 'wood' and truth by 'stone'. It has in like manner been made clear to me from the fact that when I have seen a wooden house the concept of good has instantly presented itself, and when I have seen a stone house the concept of truth has done so. And I have also learned from angels about this matter. This is why, when in the Word 'the House of God' is mentioned, the concept of good presents itself to angels, the kind of good depending on the nature of the subject that is being dealt with. And when 'the Temple' is mentioned, the concept of truth presents itself, the kind of truth depending on the subject that is being dealt with. From this one may also deduce how deeply and inwardly concealed the heavenly arcana lie in the Word.

[3] The reason 'the House of God' here means the Lord's kingdom as it exists in the ultimate degree of order is that the subject is Jacob who, as often shown already, represents the Lord's Divine Natural. The natural exists in the ultimate degree of order, for the natural encompasses all interior degrees and includes them all together within itself. And since they are included all together within the natural, and so countless things are beheld as a single whole, obscurity exists there compared with other degrees. This obscurity too has been dealt with frequently.