Musnad Ahmad 415:3

Abdullah ibn Ahmad said: Ahmad ibn Hatim al-Tawil—who was a trustworthy, righteous man—narrated to us, saying: Abd al-Aziz ibn Muhammad, meaning al-Darawardi, narrated to us, from Amr ibn Yahya, from his father or his uncle, who said: "I had a lock of hair, and whenever I prostrated, I would lift it up. Abu Hasan al-Mazini saw me and said: 'You lift it up so that the dust does not touch it? By Allah, I will surely shave it off.' So he shaved it off."