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.

7010. 'And you will be for him as a god' means Divine Truth that goes forth directly from the Lord. This is clear from the representation of 'Moses' as the Lord in respect of Divine Truth, dealt with in 6752. Its being the Divine Truth which goes forth directly from the Lord is what is meant by the declaration that he was to be for Aaron as a god. For in the Word 'God' is used to mean the Lord with regard to Divine Truth, and 'Jehovah' to mean the Lord with regard to Divine Good.

In the Word the Lord is called 'God' when the subject is truth, but 'Jehovah' when the subject is good, see 2586, 2769, 2807, 2822, 3921 (end), 4402.

Angels are called 'gods' because of the truths from the Lord which guide them, 4402.

And in the contrary sense 'the gods of the nations' are falsities, 4402 (end), 4544.