Matthew Henry Commentary Leviticus 9:22-24

"And Aaron lifted up his hands toward the people, and blessed them; and he came down from offering the sin-offering, and the burnt-offering, and the peace-offerings. And Moses and Aaron went into the tent of meeting, and came out, and blessed the people: and the glory of Jehovah appeared unto all the people. And there came forth fire from before Jehovah, and consumed upon the altar the burnt-offering and the fat: and when all the people saw it, they shouted, and fell on their faces." — Leviticus 9:22-24 (ASV)

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 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 its lusts, is a sure sign of God's gracious acceptance of our persons and actions. Nothing goes to God except what comes from him.

We must have grace, that holy fire, from the God of grace; otherwise, we cannot serve him acceptably (Hebrews 12:28). The people were moved by this revelation of God's glory and grace. They received it with the highest joy, triumphing in the assurance given them that they had God near to them. And with the lowest reverence, humbly adoring the majesty of that God, who graciously chose to manifest himself to them in this way.

That is a sinful fear of God, which drives us from him; a gracious fear makes us bow before him.