On the authority of Abu Mas'ud 'Uqba ibn 'Amr al Ansari al Badri (may Allah be pleased with him), who said: The Messenger of Allah* said:
Among the words people obtained from the First Prophecy1 are: If you feel no shame, then do as you wish2.
Related by al Bukhari.
1. From the Prophets who preceded Muhammad*.
2. This Hadith can be interpreted in two ways a) that one may act safely according to his own conscious so long as he feels no shame, and b) that if one is not capable of any feeling of shame there is nothing to prevent one from behaving as one likes i.e badly.