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.

8344. Verses 22-26 And Moses caused Israel to travel on from the Sea Suph, and they went out to the wilderness of Shur; and they went three days in the wilderness and did not find water. And they came to Marah, and they could not drink the waters for bitterness; for they were bitter. Therefore he called the name of it Marah. And the people grumbled against Moses, saying, What shall we drink? And he cried to Jehovah; and Jehovah showed him [some] wood, and he threw it into the waters, and the waters became sweet. There He established for him a statute and a judgement, and there He tempted him. And He said, If you obediently hear the voice of Jehovah your God, and do what is right in His eyes, and hearken to His commandments, and keep all His statutes, I will not put on you any sickness that I put on the Egyptians; for I, Jehovah am your Healer.

'And Moses caused Israel to travel on from the Sea Suph' means a further stage in accordance with the order made known by God's truth, after they had passed through a region of hell. 'And they went out to the wilderness of Shur' means a state of temptation into which they were led after that. 'And they went three days in the wilderness and did not find water' means that truths were lacking, and at length were plainly so. 'And they came to Marah' means a state of temptation. 'And they could not drink the waters for bitterness; for they were bitter' means that truths seemed to them to be unpleasant, as being devoid of an affection for good. 'Therefore he called the name of it Marah' means the state and essential nature of that temptation. 'And the people grumbled against Moses' means grief caused by the bitterness of the temptation. 'Saying, What shall we drink?' means that they cannot tolerate truths because, as a result of their lack of affection [for good], they find them unpleasant. 'And he cried to Jehovah' means pleas made to the Lord as a result of the grief. 'And Jehovah showed him [some] wood' means that the Lord instilled good. 'And he threw it into the waters' means with which he suffused the truths. 'And the waters became sweet' means that as a result the truths were made pleasant. 'There He established for him a statute and a judgement' means the truth of order, such as was revealed at that time. 'And there he tempted him' means in respect of temptations in general. 'And He said' means instruction. 'If you obediently hear the voice of Jehovah your God' means faith in the Lord's commandments. 'And do what is right in His eyes' means a life in keeping with them. 'And hearken to His commandments' means obedience and a life in keeping with forms of the good of faith, which are interior aspects of the Church. 'And keep all His statutes' means a life in keeping with the truths of faith, which are exterior aspects of the Church. 'I will not put on you any sickness that I put on the Egyptians' means that they are to be withheld from the evils present among those who uphold separated faith and lead a life of evil. 'For I, Jehovah, am your Healer' means that the Lord alone preserves them from evils.