Sahih Bukhari
Good Manners and Form (Al-Adab)
Volume: 008 / Book Number: 073 / Hadith Number: 141
Narrated Abu Mas'ud:
The Prophet said, 'One of the sayings of the early Prophets which the people have got is: If you don't feel ashamed do whatever you like." (See Hadith No 690, 691, Vol 4)