Altar
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.
Numbers 34:17-28
17
"These are the names of the men who shall divide the land to you for inheritance: Eleazar the priest, and Joshua the son of Nun.
18
You shall take one prince of every tribe, to divide the land for inheritance.
19
These are the names of the men: Of the tribe of Judah, Caleb the son of Jephunneh.
20
Of the tribe of the children of Simeon, Shemuel the son of Ammihud.
21
Of the tribe of Benjamin, Elidad the son of Chislon.
22
Of the tribe of the children of Dan a prince, Bukki the son of Jogli.
23
Of the children of Joseph: of the tribe of the children of Manasseh a prince, Hanniel the son of Ephod.
24
Of the tribe of the children of Ephraim a prince, Kemuel the son of Shiphtan.
25
Of the tribe of the children of Zebulun a prince, Elizaphan the son of Parnach.
26
Of the tribe of the children of Issachar a prince, Paltiel the son of Azzan.
27
Of the tribe of the children of Asher a prince, Ahihud the son of Shelomi.
28
Of the tribe of the children of Naphtali a prince, Pedahel the son of Ammihud."
