It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the polytheists used to part their hair, while the People of the Book would leave them as they were. And the blessed habit of the Prophet (peace and blessings be upon him) was that in matters where no command had come, the Prophet (peace and blessings be upon him) preferred to follow and agree with the People of the Book rather than the polytheists. Therefore, the Prophet (peace and blessings be upon him) also did not part his hair, but later he (peace and blessings be upon him) started parting his hair.