Abu Dawud Book 1, Hadith Number 31.

Chapter : Disapproval of touching the penis with the right hand while purifying.

Narated By Abu Qatadah : The Prophet (PBUH) said: when anyone of you urinates, he must not touch his penis with his right hand, and when he goes out to relieve himself he must not wipe himself with his right hand (in the privy) and when he drink, he must not drink in one breath.