Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 15
Narated By Abu Sa'id al-Khudri : I heard the Apostle of Allah (pbuh) say: When two persons go together for relieving themselves uncovering their private parts and talking together, Allah, the Great and Majestic, becomes wrathful at this (action).