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.

4602. Verses 22-26 And the sons of Jacob were twelve. The sons of Leah: Reuben, Jacob's firstborn, and Simeon, and Levi, and Judah, and Issachar, and Zebulun. The sons of Rachel: Joseph and Benjamin. And the sons of Bilhah, Rachel's servant-girl: Dan and Naphtali. And the sons of Zilpah, Leah's servant-girl: Gad and Asher. These are the sons of Jacob who were born to him in Paddan Aram.

'The sons of Jacob were twelve' means a state in which all things were now present in the Divine Natural. 'The sons of Leah' means external Divine Goods and Truths in their proper order. 'Reuben, Jacob's firstborn' means the good of faith. 'And Simeon, and Levi, and Judah, and Issachar, and Zebulun' means the essential characteristics of these. 'The sons of Rachel: Joseph and Benjamin' means interior goods and truths. 'And the sons of Bilhah, Rachel's servant-girl: Dan and Naphtali' means secondary goods and truths which serve the interior ones. 'And the sons of Zilpah, Leah's servant-girl: Gad and Asher' means those that serve the exterior ones. 'These are the sons of Jacob who were born to him in Paddan Aram' means the origin and the state of these at this point.