Judges 16:7 (KJV)

And the lords of the Philistines came up unto her, and said unto her, Entice him, and see wherein his great strength lieth, and by what means we may prevail against him, that we may bind him to afflict him: and we will give thee every one of us eleven hundred pieces of silver.

And Delilah said to Samson, Tell me, I pray thee, wherein thy great strength lieth, and wherewith thou mightest be bound to afflict thee.

And Samson said unto her, If they bind me with seven green withs that were never dried, then shall I be weak, and be as another man.

Then the lords of the Philistines brought up to her seven green withs which had not been dried, and she bound him with them.

Now there were men lying in wait, abiding with her in the chamber. And she said unto him, The Philistines be upon thee, Samson. And he brake the withs, as a thread of tow is broken when it toucheth the fire. So his strength was not known.