She fastened it with the pin, and said to him, The Philistines are on you, Samson. He awakened out of his sleep, and plucked away the pin of the beam, and the web.
The reason Samson lost his strength was only secondarily that he allowed Delilah to cut his hair. The real reason was that "the Lord had departed from him" (Judges 16:20). When God’s Spirit departed from someone under the Old Covenant, the results were disastrous (cf. 1 Samuel 16:14; Psalms 51:11).