John Gill 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)

For it was so, when Jezebel cut off the prophets of the Lord ,
&c.] Or slew them, as the Targum; put them to death some way or another; such as were brought up in the schools of the prophets, trained up in religious exercises, and instructed others therein:

that Obadiah took one hundred prophets, and hid them by fifty in a
cave ;
fifty in one cave and fifty in another; for there were large caves in the land of Israel capable of holding such a number, and many more, see (1 Samuel 22:1) (24:3) and fed them with bread and water; which in this time of famine were very acceptable; though these may be put for all the necessaries of life.