Yahya related to me from Malik from Nafi from 'Abdullah ibn 'Umarthat Umar ibn al-Khattab said, "Someone who puts plaits in his hairshould shave his head, and do not plait your hair in such a way thatit seems you have matted it." (ID)
USC-MSA web (English) reference: Book 20, Hadith 200 (ID)
Arabic reference (ID): Book 20, Hadith 899 (ID)