Once at the time of Prophet Musa (peace be upon him), there was a drought. The tribe of Israel asked him to pray for rain. Prophet Musa told them to come with him to the mountain. When they climbed the mountain he said to his people: “Whoever has committed a sin, do not follow me.” They all turned and walked back down the mountain except one man. He was blind from one eye and known to the people as Barkh.
Prophet Musa asked him, “Did you not hear what I said?” “Yes” he replied. Prophet Musa asked again, “Have you never committed a sin?” Barkh paused and then replied, “I cannot remember committing a sin except for one, but I do not know whether it is regarded a sin. I will it to you and if it is a sin I shall return.”
Prophet Musa enquired as to what it was. Barkh replied, “Once I happened to pass the door of a house which was open. I glanced in and saw somebody, but I was not able to tell whether it was a man or woman. I said to my eye, ‘Out of my whole body you hurried to commit a sin. You cannot remain with me anymore.’ So I plucked out my eye. If this is a sin I will return.”
Prophet Musa assured him that he had not sinned and then told him to pray for rain.
They prayed to Allah and both walked home in the mud.
(Taken with modifications from http://www.haqislam.org/sinless-barkh/)