What is an altar? A place of sacrifice. Practically speaking, an altar is much like a grill. It was a place where a fire was lit and on which things were burned. Symbolically, however, an altar is a mountain. It stands on the ground where human beings are and raises things up to the skies. From the altar the smoke of the burnt offerings went up. The altar was much like mount Sinai, to which the people approached, and on the smoking top of which God came down. Sacrifices were symbolic meals, and it was on the altar that the choice portion that belonged to God was consumed. It was God’s place at the table, in that sense.
The bronze altar was 7 ½ ft square, and 4 ½ ft high. Its construction was such that it was hollow, and was probably filled with earth and stones, which insulated the bronze covered board of the frame. It had horns on each of the corners, and these represented the power of the altar. Blood was daubed on these horns in cleansing rituals. It also consecrated things. We read, when it is finally dedicated, that whatever touched it would be made holy, or devoted, or consecrated. That means that whatever touched it became the Lord’s possession, no longer useful for common purposes but for special, consecrated purposes. It was a warning to use it only for holy purposes.
That it was bronze is associated with the lowest order of the precious metals of the temple, the level that touched the ground at the borders of the encampment. This bronze altar was set in the courtyard, the enclosure which set off the holy space of God’s dwelling from the space of his people’s dwelling and where God’s people could come with their gifts of devotion, of cleansing, of communion. God received the gifts brought from the life of his people. They were prepared and in contact with the altar, consecrated so they might be received by a holy God. Holiness to the Lord, was the legend on the High Priest’s crown: and only holy things would be received.
That altar represents Jesus Christ, who is not only the sacrifice and the one sacrificing as high priest. Jesus Christ is that which consecrates us, the one who is not only clean, but cleansing. In union with him we are consecrated, devoted to the Lord and no longer available for common or profane purposes. But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God. 1 Corinthians 6:11. The words of Paul, especially what he says in the following verses 15-20 seem to me to allude to the idea of contact with holy things and how that renders one consecrated and unfit for common usage. He was thinking of the shadow of Christ in Exodus, and the meaning for us who no longer need a bronze altar of the spiritual realities the bronze altar represented. Our body and our spirit now belong to God, Paul says, and can only be used for his glory. We have come into contact with that which turns us into living sacrifices, holy, acceptable unto God.
Now this brazen altar was a type of Christ dying to make atonement for our sins: the wood would have been consumed by the fire from heaven if it had not been secured by the brass; nor could the human nature of Christ have borne the wrath of God if it had not been supported by a divine power. Christ sanctified himself for his church, as their altar (Jn. 17:19), and by his mediation sanctifies the daily services of his people, who have also a right to eat of this altar (Heb. 13:10), for they serve at it as spiritual priests. To the horns of this altar poor sinners fly for refuge when justice pursues them, and they are safe in virtue of the sacrifice there offered.
 Henry, M. (1994). Matthew Henry’s commentary on the whole Bible: complete and unabridged in one volume (pp. 133–134). Peabody: Hendrickson.