Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 6171
'Umar b. Khattab reported: I heard Allah's Messenger (may peace be upon him) as saying: Worthy amongst the successors would be a person who would be called Uwais. He would have his mother (living with him) and he would have (a small) sign of leprosy. Ask him to beg pardon for you (from Allah).