Fire came out from the presence of the LORD and consumed the burnt offering and the fat portions on the altar. And when all the people saw it, they shouted for joy and fell facedown.
We are not told what Moses and Aaron went into the tabernacle to do, Lev 9:23. Some of the Jewish writers say, "They went in to pray for the appearance of the divine glory;" most probably they went in that Moses might instruct Aaron how to do the service that was to be done there - burn incense, light the lamps, set the show-bread, etc....
Commenting on Leviticus 9:23-24
there came a fire out from . . . the Lord--A flame emanating from that resplendent light that filled the holy place flashed upon the brazen altar and kindled the sacrifices. This miraculous fire--for the descent of which the people had probably been prepared, and which the priests were enjoined never to let go out (Lev 6:13) --was a sign, not only of the acceptance...
When all the people saw, they shouted, and fell on their faces - 1. The miracle was done in such a way as gave the fullest conviction to the people of its reality. 2. They exulted in the thought that the God of almighty power and energy had taken up his abode among them. 3.