Abdullah bin Muhayriz narrates: I saw Abu Mahdhurah (may Allah be pleased with him), and he had (long) hair, so I said to him: "Why do you not have your hair trimmed?" He said: "I will not reduce hair over which the Messenger of Allah (peace and blessings be upon him) passed his hand."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6717