Then she said to him, "How can you say, 'I love you,' when your heart is not with me? You have mocked me these three times, and have not told me where your great strength lies." And it came to pass, when she pestered him daily with her words and pressed him, so that his soul was vexed to death, that he told her all his heart, and said to her, "No razor has come upon my head, for I have been a Nazirite to God from my mother's womb. If I am shaven, then my strength shall leave me, and I shall become weak like any other man." Judges 16:15-17
Of course, Samson fails to mention that he has already broken most other aspects of the Nazirite vow (detailed in Numbers 6):
1. No alcohol, vinegar, or anything from grapes (Samson threw a feast for his wedding - questionable whether he kept his vow)
2. No Shaving your head (which Delilah takes care of)
3. No going near dead bodies (Samson voluntarily comes back to fetch honey out of the dead lion)
4. If one should have a sudden death in one's vicinity, one must take seven days to cleanse oneself and then shave one's head to begin the Nazirite vow anew (Samson did not do this regarding the lion, his fresh jawbone of a donkey, or any men he killed)
Essentially, shaving the head was the final straw for Samson.
"If I am shaven, then my strength shall leave me, and I shall become weak like any other man."
However, it was not just Samson's strength than left him - in verse 20, it says,"The Lord had departed from him."
Samson's strength was not in his hair - his strength was in the Lord. By breaking his vows without atonement, he was forced into cleansing and atonement, for the Lord had left him. In time, yes, his hair grew back and the Spirit of the Lord filled him once more, but his strength truly was the Lord, not his hair. What if he had had the sense to tell Delilah the true source of his strength, that it was not in anything he was capable of doing himself, but rather in his God?
Would he have died in revenge for his eyes?
Or would the Lord have found even greater uses for a man who relied on Him for his strength?
And likewise, oughtn't we give credit where it is due? That our strengths and talents are not of ourselves, but rather of the Lord our God?