Definition and Purpose:
Incense altars in the Bible are structures specifically designed for the burning of incense, a practice deeply rooted in the worship and ritual life of ancient Israel. The burning of incense was symbolic of prayer and the presence of God, serving as a fragrant offering that ascended to the heavens. The incense altar was a central element in the tabernacle and later in the temple, signifying the continual prayers of the people rising before God.

Biblical Description:
The primary incense altar described in the Bible is the Altar of Incense located in the Holy Place of the tabernacle, and later the temple. According to Exodus 30:1-3 , "You are also to make an altar of acacia wood for the burning of incense. It is to be square, a cubit long and a cubit wide, and two cubits high. Its horns must be of one piece with it. Overlay the top and all the sides and horns with pure gold, and make a gold molding around it."

Construction and Materials:
The altar was constructed from acacia wood and overlaid with pure gold, signifying its sacred purpose and the holiness required in approaching God. It was equipped with horns on its corners, which were also overlaid with gold. The altar was placed before the veil that separated the Holy Place from the Most Holy Place, directly in front of the Ark of the Covenant, as described in Exodus 40:5 : "Place the gold altar of incense in front of the ark of the testimony, and put up the curtain at the entrance to the tabernacle."

Ritual Use:
The burning of incense was a daily ritual performed by the priests. Exodus 30:7-8 states, "And Aaron is to burn fragrant incense on it every morning when he tends the lamps. When Aaron sets up the lamps at twilight, he must burn the incense perpetually before the LORD for the generations to come." This perpetual offering symbolized the constant prayers and intercession of the people before God.

Symbolism and Significance:
Incense in the Bible is often associated with prayer and divine presence. Psalm 141:2 reflects this symbolism: "May my prayer be set before You like incense, my uplifted hands like the evening offering." The fragrant smoke ascending from the altar represented the prayers of the faithful rising to God, a pleasing aroma in His sight.

Regulations and Restrictions:
The use of the incense altar was strictly regulated. Only a specific blend of spices was to be used, as detailed in Exodus 30:34-38 , and it was not to be used for any other purpose. Unauthorized use or offering of "strange incense" was strictly forbidden, as seen in the tragic account of Nadab and Abihu in Leviticus 10:1-2 , where they offered unauthorized fire before the LORD and were consumed by fire as a result.

New Testament References:
In the New Testament, the imagery of incense continues to hold significance. In Revelation 8:3-4 , the prayers of the saints are depicted as incense before God: "Another angel, who had a golden censer, came and stood at the altar. He was given much incense to offer, along with the prayers of all the saints, on the golden altar before the throne. And the smoke of the incense, together with the prayers of the saints, rose up before God from the hand of the angel."

Conclusion:
The incense altar, with its rich symbolism and strict regulations, underscores the importance of holiness, prayer, and the presence of God in the worship life of Israel. It serves as a powerful reminder of the need for purity and reverence in approaching the divine.