It was narrated from Ibn 'Abbas that:The Messenger of Allah [SAW] used to let his hair hang down (without a parting) and the Mushrikun used to part their hair. The Messenger of Allah [SAW] liked to act in accordance with the People of the Book, in matters where no specific command had been given to him. Then the Messenger of Allah [SAW] parted his hair after that

English translation · Sunan an-Nasa'i