After preaching the Sermon on the Mount (Matthew 5-7), Jesus came down the hillside followed by a large crowd. A leper approached Jesus and was miraculously healed of his skin disease.
As described in the book of Luke, which is in the New Testament of the Bible:
Jesus reached out his hand and touched the man. "I am willing," he said. "Be clean!" And immediately the leprosy left him.
Then Jesus ordered him, "Don't tell anyone, but go, show yourself to the priest and offer the sacrifices that Moses commanded for your cleansing, as a testimony to them."
Yet the news about him spread all the more, so that crowds of people came to hear him and to be healed of their sicknesses.
- Luke 5:12-15, NIV translation.
The word "leprosy" can refer to a variety of diseases that affect a person's skin.