Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(v. 1-21) The first offerings of Aaron for himself and the people.
(Lev 9:22-24) Moses and Aaron bless the people, Fire cometh upon the altar from the Lord.
These many sacrifices, which were all done away by the death of Christ, teach us that our best services need washing in his blood, and that the guilt of our best sacrifices needs to be done away by one more pure and more noble than they. Let us be thankful that we have such a High Priest. The priests had not a day's respite from service allowed. God's spiritual priests have constant work, which the duty of every day requires; they that would give up their account with joy, must redeem time. The glory of God appeared in the sight of the people, and owned what they had done. We are not now to expect such appearances, but God draws nigh to those who draw nigh to him, and the offerings of faith are acceptable to him; though the sacrifices being spiritual, the tokens of the acceptance are spiritual likewise. When Aaron had done all that was to be done about the sacrifices, he lifted up his hands towards the people, and blessed them. Aaron could but crave a blessing, God alone can command it.
When the solemnity was finished, and the blessing pronounced, God testified his acceptance. There came a fire out from before the Lord, and consumed the sacrifice. This fire might justly have fastened upon the people, and have consumed them for their sins; but its consuming the sacrifice signified God's acceptance of it, as an atonement for the sinner. This also was a figure of good things to come. The Spirit descended upon the apostles in fire. And the descent of this holy fire into our souls, to kindle in them pious and devout affections toward God, and such a holy zeal as burns up the flesh and the lusts of it, is a certain token of God's gracious acceptance of our persons and performances. Nothing goes to God, but what comes from him. We must have grace, that holy fire, from the God of grace, else we cannot serve him acceptably, Heb 12:28. The people were affected with this discovery of God's glory and grace. They received it with the highest joy; triumphing in the assurance given them that they had God nigh unto them. And with the lowest reverence; humbly adoring the majesty of that God, who vouchsafed thus to manifest himself to them. That is a sinful fear of God, which drives us from him; a gracious fear makes us bow before him.