Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 208
Narated By 'Urwah : 'Ali b. Abi Talib said to al-Miqdad, and made a similar statement as above. Al-Miqdad asked him (the Prophet). The Apostle of Allah (may peace be upon him) said: He should wash his penis and testicles.
Abu Dawud said: The tradition has been narrated by al-Thawri and a group of narrators from Hisham on the authority of his father from al-Miqdad, from 'All reporting from the Prophet (may peace be upon him).