On the plague of Athens in 430 BC. History of the Peloponnesian War (2.52): “the catastrophe was so overwhelming that men, not knowing what would happen next to them, became indifferent to every rule of religion or law.” Thucydides continues (2.53, Warner trans.):

In other respects also Athens owed to the plague the beginnings of a state of unprecedented lawlessness (ἀνομίας). Seeing how quick and abrupt were the changes of fortune which came to the rich who suddenly died and to those who had previously been penniless but now inherited their wealth, people now began openly to venture on acts of self-indulgence which before then they had used to keep dark. Thus they resolved to spend their money quickly and to spend it on pleasure, since money and life alike seemed equally ephemeral. As for what is called honour, no one showed himself willing to abide by its laws, so doubtful was it whether one would survive to enjoy the name for it. It was generally agreed that what was both honourable and valuable was the pleasure of the moment and everything that might conceivably contribute to that pleasure. No fear of god or law of man had a restraining influence. As for the gods, it seemed to be the same thing whether one worshipped them or not, when one saw the good and the bad dying indiscriminately. As for offenses against human law, no one expected to live long enough to be brought to trial and punished: instead everyone felt that already a far heavier sentence had been passed on him and was hanging over him, and that before the time for its execution arrived it was only natural to get some pleasure out of life.