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.
Psalms 102
1
Hear my prayer, Yahweh! Let my cry come to you.
2
Don't hide your face from me in the day of my distress. Turn your ear to me. Answer me quickly in the day when I call.
3
For my days consume away like smoke. My bones are burned as a torch.
4
My heart is blighted like grass, and withered, for I forget to eat my bread.
5
By reason of the voice of my groaning, my bones stick to my skin.
6
I am like a pelican of the wilderness. I have become as an owl of the waste places.
7
I watch, and have become like a sparrow that is alone on the housetop.
8
My enemies reproach me all day. Those who are mad at me use my name as a curse.
9
For I have eaten ashes like bread, and mixed my drink with tears,
10
Because of your indignation and your wrath, for you have taken me up, and thrown me away.
11
My days are like a long shadow. I have withered like grass.
12
But you, Yahweh, will remain forever; your renown endures to all generations.
13
You will arise and have mercy on Zion; for it is time to have pity on her. Yes, the set time has come.
14
For your servants take pleasure in her stones, and have pity on her dust.
15
So the nations will fear the name of Yahweh; all the kings of the earth your glory.
16
For Yahweh has built up Zion. He has appeared in his glory.
17
He has responded to the prayer of the destitute, and has not despised their prayer.
18
This will be written for the generation to come. A people which will be created will praise Yah.
19
For he has looked down from the height of his sanctuary. From heaven, Yahweh saw the earth;
20
to hear the groans of the prisoner; to free those who are condemned to death;
21
that men may declare the name of Yahweh in Zion, and his praise in Jerusalem;
22
when the peoples are gathered together, the kingdoms, to serve Yahweh.
23
He weakened my strength along the course. He shortened my days.
24
I said, "My God, don't take me away in the midst of my days. Your years are throughout all generations.
25
Of old, you laid the foundation of the earth. The heavens are the work of your hands.
26
They will perish, but you will endure. Yes, all of them will wear out like a garment. You will change them like a cloak, and they will be changed.
27
But you are the same. Your years will have no end.
28
The children of your servants will continue. Their seed will be established before you." By David.
