Albert Barnes Commentary 1 Kings 18:4

"for it was so, when Jezebel cut off the prophets of Jehovah, that Obadiah took a hundred prophets, and hid them by fifty in a cave, and fed them with bread and water.)" — 1 Kings 18:4 (ASV)

We have no details of Jezebel’s bloody deed. Some have speculated that it was Jezebel’s response to Elijah’s threat, and that the command given to him to hide in Cherith alone saved him from being one of the victims. This view receives some support from the actions and words of Obadiah (1 Kings 18:13).

Fifty in a cave—The limestone formation of Judea and Samaria abounds with large natural caverns, the size of which was easily increased by human effort. These “caves” played an important part in the history of the country, serving especially as refuges for political offenders and other fugitives (Judges 6:2; 1 Samuel 13:6; Hebrews 11:38).