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.

4981. 'And the blessing of Jehovah was' means increases. This is clear from the meaning of 'the blessing of Jehovah'. In the genuine sense 'the blessing of Jehovah' means love to the Lord and charity towards the neighbour, for those who are endowed with these are called 'the blessed of Jehovah' since they are in that case endowed with heaven and eternal salvation. Consequently 'the blessing of Jehovah' in the external sense, that is, in the sense which has to do with a person's state in the world, means resting content in God and on that account being content with one's position in society and with the amount of wealth one possesses, whether one is among the highly honoured and is wealthy or among the not so honoured and the poor. For the person who rests content in God regards positions and wealth as means to fulfill useful purposes; and when he thinks about these and at the same time about eternal life, he rates them as nothing and eternal life as that which is essential.

[2] Because 'the blessing of Jehovah (or the Lord)' implies such increases in the genuine sense, blessing also implies countless other benefits and consequently means the various gifts which flow from it, such as enrichment with spiritual and celestial good, 981, 1731; fruitfulness resulting from the affection for truth, 2846; undergoing rearrangement into heavenly order, 3017; being endowed with the good of love and thereby being joined to the Lord, 3406, 3504, 3514, 3530, 3584; and joy, 4216. What is meant by 'blessing' therefore in any specific instance becomes clear from the context in which it appears. Here the meaning of 'the blessing of Jehovah' as increases in good and truth, that is, in life and doctrine, is evident from what follows it, for there it says that this blessing of Jehovah was 'in the house and in the field', and 'house' means good which is the good of life, while 'field' means truth which is the truth of doctrine. From this it is evident that increases in these are meant in this case by 'the blessing of Jehovah'.