In 1 Kings 18 God through Elijah opened up the heavens to rain. Both the shutting up of heaven from rain and the opening of heaven to rain were great things.
God sent Elijah to see Ahab and to tell him that God would send rain upon the earth, and Elijah went to appear before Ahab (vv. 1-2). In coming to Ahab Elijah was very bold.
Ahab came to meet Elijah through Obadiah, a servant of Ahab who hid a hundred prophets and fed them when Jezebel, Ahab's wife, cut off the prophets of Jehovah (vv. 3-16). Ahab and Elijah were enemies, and Obadiah was the middle man between them.
Elijah challenged Ahab to have a test on Mount Carmel and prove who is the real God—Baal of the heathens or Jehovah of Israel (vv. 17-40).
Ahab, unable to avoid this challenge, sent word and gathered all of Israel to him at Mount Carmel, as well as the 450 prophets of Baal and the 400 prophets of Asherah, who ate at Jezebel's table. The prophets of Baal offered a bullock to Baal and begged Baal to burn their offering, crying and even cutting themselves so that their blood gushed out. They did all this to no avail as Elijah mocked them (vv. 17-29).
Elijah, by himself alone, repaired (recovered) the broken-down altar of Jehovah by building it unto the name of Jehovah with twelve stones (signifying Israel, God's elect). Then he dug a trench around the altar with a capacity deep and wide, cut the bullock in pieces and laid it on the wood, and poured four jars of water on the burnt offering and on the wood three times until the water went around the altar and filled the trench also with water. After this, Elijah prayed to God, and Jehovah sent fire to consume the burnt offering, the wood, the stones, and the dust and to lick up the water that was in the trench (vv. 30-38).