Yahya related to me from Malik from Zayd ibn Aslam that Ata ibn Yasar told him that the Messenger of Allah, may Allah bless him and grant him peace, was in the mosque when a man came in with dishevelled hair and beard. The Messenger of Allah. may Allah bless him and grant him peace, motioned with his hand that he should be sent out to groom his hair and beard. The man did so and then returned. The Messenger of Allah, may Allah bless him and grant him peace, said, "Isn't this better than that one of you should come with his head dishevelled, as if he were a shaytan?"

Muwatta Malik Book 51, Hadith 7