Praised be Jesus and Mary, now and forever.
Jesus introduces many new teachings in the Sermon on the Mount, and yet these are in continuity with the Law and the Prophets. So lest his new and authoritative teaching be misunderstood, he says, do not think I have come to abolish the Law or the Prophets. I have come not to abolish, but to fulfill. 
The fulfillment of the Law is in continuity with the Law, but goes beyond it, and in going beyond sets aside ceremonial precepts which prefigure the grace and sacraments he brings, that our Lord brings. As a sign of this continuity, when he was transfigured on the mountain, he appeared with Moses and Elijah. 
In the passage we heard from the first Book of Kings, Elijah has a dramatic showdown with the Prophets of Baal. The drought has gone on for three years, and the time is ripe to bring the Israelites back to the Lord. So God told Elijah, go, show yourself to Ahab, and I will send rain upon the earth. So the Prophet came out of hiding and sought a meeting with the King.
In the countryside he ran into Obadiah. This is not the Prophet of that name who lived centuries later, but the man whom Ahab had sent over his household, the highest position after the King in the kingdom. He was a good man who was hiding a hundred Prophets of the Lord in caves. So Elijah sent him to ask Ahab for a meeting. Ahab came willingly because he had been searching the land for Elijah during the drought. He wanted to get rid of him, hoping that would get rid of the drought. 
When Ahab saw Elijah, Ahab said to him, is it you, you troubler of Israel? And he answered, I have not troubled Israel, but you have, and your father's house, because you have abandoned the commandments of the Lord and followed the Baals. So while Ahab blames Elijah for the drought because it was imposed at his word, Elijah tells Ahab that he's really the one responsible for it. In fact, it is the worship of Baal idols that made it necessary for God to resort to this severe measure. And it is a drought precisely because the idol being worshipped is Baal, the storm god. The Lord is trying to demonstrate that Baal is no God and is not really the one responsible for sending rain. 
But three years of drought, three years of failed invocations by the Prophets of Baal were not enough to make that message sink in. So it's time for a showdown. Elijah tells Ahab what he wants, gather all Israel at Mount Carmel and the 450 Prophets of Baal and the 400 Prophets of Asherah, Baal's consort, who eat at Jezebel's table. Mount Carmel was on the border between Israel and Phoenicia, between the land the Lord had promised and a pagan land, the land of Jezebel that had long worshipped Baal. Mountains were often sacred places and this mountain range, covered by lush vegetation, a little less lush during the drought, was likely a site for Baal worship. 
Elijah began by appealing to the people. How long will you straddle the issue? If the Lord is God, follow him. If Baal, follow him. No one can serve two masters, as our Lord said. 
But they don't want to choose. Maybe they like the immoral Canaanite cult. Maybe they're afraid to abandon a God that has royal patronage. In any case, they need convincing. So Elijah issues his challenge. Each side will emulate a young bull and lay the pieces on wood, but it will be up to the God to start the fire. 
When the Prophet says, I am the only surviving Prophet of the Lord, there's some hyperbole in that, because Obadiah is hiding a hundred Prophets in a cave. But it's true that Elijah is the only one left on the field. The Storm God has 450 Prophets, Prophets so prestigious that they have royal patronage. They ought to be able to get him to send one lightning bolt to ignite the wood. 
The people agree to the challenge, one way or the other it's going to be an interesting day. There's also a specific purpose to holding this challenge before God ends the drought. For three years now, Baal's worshippers have been asking him for rain, because the crops need it so desperately. And the Lord's worshippers have been asking him for rain. Some people have doubtless been asking both. Sending fire is a sign that the God has accepted the sacrifice, and so will grant the petition for rain. So the challenge also serves to make sure that when the rain comes, the right God gets credit for it. 
Elijah has really been sent by God, so he's certain what will happen. He lets the Prophets of Baal go first. He doesn't want them to have any excuse for the failure of their God to answer. When noon comes and goes with no fire, he mocks them and they get more serious and begin cutting themselves. This is a mourning ritual. In Canaanite myth, lack of rainfall corresponded to Baal being taken away by the God of death. His prophets mourn him so that he will escape and bring rain again.
When the time comes for offering the evening sacrifice in the temple of the Lord, Elijah prepares the sacrifice to the Lord. He sets up an altar of 12 stones to renew the worship of the Lord by all 12 tribes to set up that worship again. Confident in God's power, he even has the sacrifice doused with water three times, so that the water fills a trench around the altar. Then he addresses a simple petition to God, asking for the fire as a sign that he has been acting on God's orders.
The response is immediate and dramatic. The Lord's fire came down and consumed the burnt offering, wood, stones, and dust, and it lapped up the water in the trench. All the people fell prostrate in adoration, saying, the Lord is God, the Lord is God. They finally accepted the message expressed by Elijah's name, which means, the Lord is my God. 
This is a high point in the prophet's life. He has brought the people back to the Lord, at least for the moment, and wiped out the prophets of Baal, who pay the price set in the book of Deuteronomy for spreading a false religion. 
The Fathers of the Church teach us the deeper significance of these events. St. Basil connects the water with baptism. Elijah demonstrated the power of baptism, he writes, when he used water instead of fire to consume the sacrifice on the altar. Fire and water work at cross purposes, but when the water, a figure of the mystery, that is, of the mystery of baptism, was sprinkled three times on the altar, it flamed up as if fed by oil. Similarly, in baptism, water is poured three times, and the fire of the Holy Spirit comes down. 
The Catechism explains fire symbolizes the transforming energy of the Holy Spirit's actions. The prayer of the prophet Elijah, who arose like fire, and whose word burned like a torch, brought fire down from heaven on the sacrifice on Mount Carmel. This event was a figure of the fire of the Holy Spirit, who transforms what he touches. 
St. Ephraim connects the fire with the Eucharist. He sings, fire came down and consumed the sacrifices of Elijah. The fire of mercy has become for us a living sacrifice. Fire consumed the offering. Your fire, O our Lord, we have eaten in your offering. Eucharistic prayers call down the Holy Spirit twice, once to transform the gifts and again to transform the worshipers. The gifts of bread and wine have transformed to become the sacrifice acceptable to the Lord, the sacrifice of Calvary. The worshipers, you and I, should be offering themselves as a living sacrifice. The Holy Spirit gradually transforms them, transforms us in the measure that we are willing. 
Praised be Jesus and Mary, now and forever.