Albert Barnes Commentary 1 Kings 18:24

"And call ye on the name of your god, and I will call on the name of Jehovah; and the God that answereth by fire, let him be God. And all the people answered and said, It is well spoken." — 1 Kings 18:24 (ASV)

The God that answers by fire—God had frequently consumed offerings with supernatural fire before (Leviticus 9:24; Judges 6:21). The Baal-worshippers were no doubt in the habit of attributing thunder and lightning to their gods—the great Nature-power—and thus had no excuse for declining Elijah’s challenge.