The Philistines laid hold on him, and put out his eyes; and they brought him down to Gaza, and bound him with fetters of brass; and he did grind in the prison-house.
The fact that Samson told Delilah to do something to his hair (Judges 16:13) suggests that he was giving her a clue to his strength. She did not pick this up but kept hounding him for his secret. Finally he gave in (Judges 16:17; cf. Judges 14:17).