How did Elijah prove that Jehovah was God on Mount Carmel?
Elijah proved Jehovah was God by setting up a test on Mount Carmel: after Baal's prophets called out with no response, Elijah called on Jehovah, the God of Israel. Fire came down and consumed the sacrifice, even licking the water out of the trenches, demonstrating Jehovah's power before Israel.
Les explains that on Mount Carmel Elijah prepared a test for the prophets of Baal. They were told to call on their god to devour the sacrifices, but nothing happened. Elijah taunted them, saying to yell louder because their gods were sleeping, and still nothing happened. Then Elijah called on Jehovah, the God of Israel. Fire came down and did not just consume the sacrifices, but literally licked the water out of the trenches. By this, Elijah proved to Israel that Jehovah was still the God of Israel. Les also notes that afterward Elijah demanded the 400 prophets of Baal be killed, and they were. A messenger then went from Mount Carmel to Jezreel and told Jezebel, who threatened Elijah's life. Despite such manifestations of Jehovah's power, Israel could quickly sink into unbelief, and even Elijah did.