and with the stones he built an altar in the name of the LORD. And he made a trench about the altar, as great as would contain two seahs of seed.
Ahab and the people expected that Elijah would, in this solemn assembly, bless the land, and pray for rain; but he had other work to do first. The people must be brought to repent and reform, and then they may look for the removal of the judgment, but not till then. This is the right method.
Commenting on 1 Kings 18:21-40
And he said, do it the second time, and they did it the second time,.... That is, poured four barrels of water more upon the wood: and he said, do it the third time, and they did it the third time; so that there were in all twelve barrels of water poured on the wood, agreeably to the number of the twelve stones the altar...
He made a trench - This was to detain the water that might fall down from the altar when the barrels should be poured upon it, Kg1 18:35.