Uncut hair was the only vow Sampson ever kept; he drank, he murdered 30 men and stripped clothing from their dead bodies, and he slept with prostitutes. In spite of all the things he did that were unrighteous, he never cut his hair. Think about why that might have been.
Did he really believe that longhair would make him righteous? Some scholars seem to think that the part of the Nazirite vow pertaining to uncut hair must have been more important than the rest. That is contrary to what Paul teaches in Romans. He teaches that when you break one part of the law you have broken all the law.. Paul also teaches that righteousness is about relationship, and not about keeping the letter of the law. In spite of all the many times Sampson’s behavior was unrighteous, God was patient and did not abandon him. God, by remaining with him was maintaining the relationship.
Perhaps Sampson did not cut his hair because it was an outward sign that could be seen by all the people and he wanted to appear to be godly. Most of his ungodly actions took place outside of the sight of his fellow Israelites. When he wanted to visit prostitutes he went to Gaza, a Philistine city. When he murdered the men and stripped their bodies it was in a Philistine city. Sampson believed that as long as he did not cut his hair, the strength of God would remain with him. It does not appear that Sampson realized that uncut hair was intended to be an outward sign of an inward condition. It was to be a visible sign to the world that he had made an inner heart commitment to serving God. His uncut hair could not make him righteous.
Sampson did not lose his strength because his hair was cut. He lost his strength because he had reached the end of God’s patience and mercy, and the Spirit of the Lord left him. Outward signs are worthless without the inner work.