Abu Dawud Book 34, Hadith Number 4504.
Narated By Abdullah ibn Amr ibn al-‘As : A man came to the Prophet (PBUH) crying for help. He said: His slave-girl, Apostle of Allah! He said: Woe to you, what happened with you ? He said that it was an evil one. He saw the slave-girl of his master; he became jealous of him, and cut off his penis. The Apostle of Allah (PBUH) said: Bring the man to me. The man was called, but people could not get control over him. The Apostle of Allah (PBUH) then said: Go away, you are free. He asked: Apostle of Allah! upon whom does my help lie? He replied: On every believer, or he said: On every Muslim.
Abu Dawud said: The name of the man who was emancipated was Rawh b. Dinar.
Abu Dawud said: The man who cut off the penis was Zinba’.
Abu Dawud said: This Zinba’ Abu Rawh was master of the slave.