Judges 16:8-9

So the Philistine tyrants brought Delilah seven new bowstrings, and she tied Samson up with them. With men waiting in ambush in one of the inner rooms of her house, she cried out, “Samson! The Philistines are here to capture you!” But Samson snapped the bowstrings like a piece of string snaps when it is burned by a fire. So no one discovered the secret of his strength.