Exodus 27:4

Thou shalt make for it a grate of net-work This was the principal part of the altar. It was let into the hollow about the middle of it, and here the fire was kept, and the sacrifice burned. It was a broad plate of brass full of holes, like a net or sieve, and partly hollow that the fire might burn the better, and the ashes might fall through to the bottom of the altar, where there was a door on the east side to open and take out the ashes.

Now this brazen altar was a type of Christ dying to make atonement for our sins. Christ sanctified himself for his church as their altar, (John 17:19,) and by his mediation sanctifies the daily services of his people. To the horns of this altar poor sinners flee for refuge, and are safe in virtue of the sacrifice there offered.