John Calvin Commentary Leviticus 9:23

"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." — Leviticus 9:23 (ASV)

And Moses and Aaron went into the tabernacle. This is a repetition of the same statement, except that what had been said of Aaron only is now also ascribed to Moses; that is, that he blessed the people, but for a different reason. For although he was God’s prophet, Aaron, by right of his office, was the only mediator.

What follows, the glory of the Lord appeared, may be read separately—namely, that the majesty of God was manifested in some conspicuous sign; or else it is connected with the concluding verse, where it is said that there came a fire out from before the Lord, etc. If we prefer the latter, the account of the consuming of the sacrifice was added as an explanation, as if it were said that God appeared when He sent forth the fire to consume the sacrifice.

By this sign, or rather miracle, God manifested that He was the Author of the legal priesthood, so that it should be held in reverence forever.

The same thing sometimes occurred afterwards when, in troubled circumstances, extraordinary confirmation was needed. For example, fire consumed the sacrifice of Manoah (Judges 13:20); or when God’s service and pure religion required to be vindicated against superstitious counterfeits, the sacrifice of Elijah was utterly consumed and reduced to ashes without the application of fire (1 Kings 18:38). Or, lastly, when God would show that He delighted in Mount Zion, which He had chosen for His resting-place and home; for this reason, the first sacrifice of Solomon was consumed by fire from heaven (2 Chronicles 7:1).

Lest posterity should doubt this matter, as if it were not thoroughly certain, Moses says that the whole people were stirred up by the sight to praise God and fell on their faces.