Charles Spurgeon Commentary 1 Kings 18:38-40

"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. And when all the people saw it, they fell on their faces: and they said, Jehovah, he is God; Jehovah, he is God. and Elijah said unto them, Take the prophets of Baal; let not one of them escape. And they took them; and Elijah brought them down to the brook Kishon, and slew them there." — 1 Kings 18:38-40 (ASV)

And thus he proved that he was the prophet of God, and that God was the God of Israel.