Abu Dawud
Combing The Hair
Book Number: 028 / Hadith Number: 4190
Narated By Abdullah ibn Amr ibn al-'As : The Apostle of Allah (pbuh) said: Do not pluck out grey hair. If any believer grows a grey hair in Islam, he will have light on the Day of Resurrection. (This is Sufyan's version). Yahya's version says: Allah will record on his behalf a good deed for it, and will blot out a sin for it.