Albert Barnes Commentary 1 Kings 18:38

"Then the fire of Jehovah fell, and consumed the burnt-offering, and the wood, and the stones, and the dust, and licked up the water that was in the trench." — 1 Kings 18:38 (ASV)

The fire of the Lord fell - This cannot have been a flash of lightning. It was altogether miraculous, both in its nature and in its opportuneness. For the people's conduct, compare the cross-references.