Judges 16:17-19

17Finally, Samson told her his secret. He said to her, ‘No one has ever cut my hair. Even before I was born, I belonged to God as a Nazirite. If someone cuts off my hair, I would have no more strength. I would become as weak as any other man.’

18Delilah realized that Samson had told her the truth. So she sent a message to the rulers of the Philistines. She told them, ‘Samson has now told me his secret. So come back once more.’ So the Philistine rulers went to visit Delilah again. They took their pieces of silver with them.

19Delilah made Samson sleep with his head on her knees. She called a man to come and he cut off the seven tails of Samson's hair. This made Samson helpless, so that he had no more strength.