Matthew Henry Commentary Exodus 27:1-8

"And thou shalt make the altar of acacia wood, five cubits long, and five cubits broad; the altar shall be foursquare: and the height thereof shall be three cubits. And thou shalt make the horns of it upon the four corners thereof; the horns thereof shall be of one piece with it: and thou shalt overlay it with brass. And thou shalt make its pots to take away its ashes, and its shovels, and its basins, and its flesh-hooks, and its firepans: all the vessels thereof thou shalt make of brass. And thou shalt make for it a grating of network of brass: and upon the net shalt thou make four brazen rings in the four corners thereof. And thou shalt put it under the ledge round the altar beneath, that the net may reach halfway up the altar. And thou shalt make staves for the altar, staves of acacia wood, and overlay them with brass. And the staves thereof shall be put into the rings, and the staves shall be upon the two sides of the altar, in bearing it. Hollow with planks shalt thou make it: as it hath been showed thee in the mount, so shall they make it." — Exodus 27:1-8 (ASV)

In the court before the tabernacle, where the people attended, was an altar, to which they must bring their sacrifices, and on which their priests must offer them to God. It was made of wood overlaid with brass. A grate of brass was set into the hollow of the altar, in the middle of which the fire was kept, and the sacrifice burned. It was made of network, like a sieve, and was suspended with a hollow space beneath it, so that the ashes could fall through.

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 Divine power.