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.

59. 31. I am returned to Jerusalem with mercies: my house shall be built in it. Jehovah of Hosts shall yet choose Jerusalem (Zechariah 1:16-17).

I saw a man with a measuring line in his hand. He said, I go to measure Jerusalem to see what is the breadth thereof and what is the length thereof. For I, saith Jehovah, will be unto Jerusalem a wall of fire round about, and I will be the glory in the midst of her. Jehovah shall choose Jerusalem again (Zechariah 2:1-12).

Jehovah chooseth Jerusalem; is not this a brand snatched from the fire (Zechariah 3:2)?

Jehovah said, I will remove the iniquity of the land in one day. In that day shall ye call, a man to his neighbor, under the vine and under the fig tree (Zechariah 3:9-10).

Thus said Jehovah; I will return to Zion and dwell in the midst of Jerusalem; therefore Jerusalem shall be called a city of truth, and the mountain of Jehovah of Hosts the mountain of holiness. The streets of the city shall yet be filled with boys and girls playing in the streets thereof. I will bring them that they may dwell in the midst of Jerusalem, that they may be My people, and I may be their God, in truth and justice. Thus many people shall come to seek Jehovah of Hosts in Jerusalem, to entreat the faces of Jehovah (Zechariah 8:2-5, 8, 12, 15, 20-22).

In that day all the nations of the earth shall be gathered together against Jerusalem. In that day shall Jehovah protect the inhabitant of Jerusalem. The house of David shall be as God, as the angel of Jehovah before them. In that day I will seek to destroy all the nations that come against Jerusalem. But I will pour upon the house of David, and upon the inhabitant of Jerusalem the spirit of grace and of prayers, that they may look upon Me whom they pierced (Zechariah 12:3, 8-10).

In that day there shall be a fountain opened to the house of David, and to the inhabitants of Jerusalem. In that day I will cut off the names of the idols out of the land, and I will cause the unclean spirit to pass out of the land (Zechariah 13:1-2).

It shall be one day which is known unto Jehovah, not day nor night; for about evening time it shall be light. And it shall be in that day that living waters shall go out from Jerusalem, in summer and in winter. And Jehovah shall be King over all the earth: in that day shall Jehovah be one, and His name one. There shall be no more curse upon the earth, but Jerusalem shall dwell securely (Zechariah 14:6-9, 11). In that day there shall be no more the Canaanite in the house of Jehovah (verse 21).

(All the gates of Zion are devastated (Lamentations 1:4). Jehovah hath turned me back; He laid me waste (verse 13). My sons are devastated (verse 16). Devastation and breaking are come upon us (Lamentations 3:47).

Thine iniquity is consummated, He will visit thine iniquity. He will manifest thy sins (Lamentations 4:22).