Abu Dawud Book 28, Hadith Number 4185.

Narated By Anas ibn Malik : Al-Hajjaj ibn Hassan said: We entered upon Anas ibn Malik. My sister al-Mughirah said: You were a boy in those days and you had two locks of hair. He (Anas) rubbed your head and invoked blessing on you. He said: Shave them (i.e. the locks) or clip them, for this is the fashion of the Jews.