'Fifties' in the Bible

had taken 100 prophets and had hidden them by fifties in a cave, providing them with food and water when Jezebel was trying to destroy the LORD's prophets.

Hasn't anyone told you, my master, what I did when Jezebel was killing the LORD's prophets? I hid 100 of the LORD's prophets by fifties in a cave and provided food and water for them.