Imam Ja’far As-Sadiq (as) says that one day Amir’ul-Mu’mineen ‘Ali (as) was sitting with his companions when a person came and said, “O Amir’ul-Mu’mineen (as)! I have committed a foul act with a boy. Please make a pronouncement against me!” Amir’ul-Mu’mineen ‘Ali (as) said, “Go away from here! Are you mad!”
The man was adamant and raised the same call four times. Amir’ul-Mu’mineen ‘Ali (as) said: You are a self confessed criminal! The Prophet (S) has ordered three punishments for such crimes!) Beheading with a sword. 2) Tying of the limbs with rope and throwing from the top of a hill. 3) Burning the person. Now tell me which of the punishments you would prefer. The man asked, “Which punishment is the most severe!” Amir’ul-Mu’mineen ‘Ali (as) said, “Getting burnt alive is the most severe!” The man cried and said, ‘I would like to be burnt alive!” A fire was lighted in a ditch and the man went crying toward it. Amir’ul-Mu’mineen ‘Ali (as) too cried in sympathy with the man and said, “You have made the angels in the Firmament cry for you! Allah in his Munificence has pardoned you!”
Reference :Ain-Al Hayat, The Essence of Life