As God intended in the tabernacle to manifest his presence among his people, so there they were to pay their devotions to him, not in the tabernacle itself (into that only the priests entered as God's domestic servants), but in the court before the tabernacle, where, as common subjects, they attended. There an altar was ordered to be set up, to which they must bring their sacrifices, and on which their priests must offer them to God: and this altar was to sanctify their gifts. Here they were to present their services to God, as from the mercy-seat he gave his oracles to them; and thus a communion was settled between God and Israel. Moses is here directed about, 1. The dimensions of it; it was square, Exo 27:1. 2. The horns of it (Exo 27:2), which were for ornament and for use; the sacrifices were bound with cords to the horns of the altar, and to them malefactors fled for refuge. 3. The materials; it was of wood overlaid with brass, Exo 27:1, Exo 27:2. 4. The appurtenances of it (Exo 27:3), which were all of brass. 5. The grate, which was let into the hollow of the altar, about the middle of it, in which the fire was kept, and the sacrifice burnt; it was made of network like a sieve, and hung hollow, that the fire might burn the better, and that the ashes might fall through into the hollow of the altar, Exo 27:4, Exo 27:5. 6. The staves with which it must be carried, Exo 27:6, Exo 27:7. And, lastly, he is referred to the pattern shown him, Exo 27:8.
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 (Joh 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.

Thou shalt make for it a grate - Calmet supposes this altar to have been a sort of box, covered with brass plates, on the top of which was a grating to supply the fire with air, and permit the ashes to fall through into the siroth or pan that was placed below. At the four corners of the grating were four rings and four chains, by which it was attached to the four horns; and at the sides were rings for the poles of shittim wood with which it was carried. Even on this there is a great variety of opinions.

And thou shalt make staves for the altar, staves of shittim wood,.... Like those that were made for the ark, and for the same purpose:

and overlay them with brass; with plates of brass, whereas those for the ark were overlaid with gold.

staves . . . rings--Those rings were placed at the side through which the poles were inserted on occasions of removal.