Musannaf Ibn Abi Shayba 27:706

Abu Usama narrated to us, he said: Sulayman ibn al-Mughirah narrated to us, from al-Jariri, from Abu Nadra, from Usayr ibn Jabir, from Umar, from the Prophet, peace and blessings of Allah be upon him, that he said: "A man will come to you who is called Uways. He had a white spot [leprosy/vitiligo], so he supplicated to Allah regarding it, and Allah removed it from him. So whoever among you meets him, command him to ask forgiveness for you." He said: So Umar met him and said, "Ask forgiveness for me," so he asked forgiveness for him.