On Clemency, Book I, XVIII

It is creditable to a man to keep within reasonable bounds in his treatment of his slaves.

Even in the case of a human chattel one ought to consider, not how much one can torture him with impunity, but how far such treatment is permitted by natural goodness and justice, which prompts us to act kindly towards even prisoners of war and slaves bought for a price (how much more towards freeborn, respectable gentlemen?), and not to treat them with scornful brutality as human chattels, but as persons somewhat below ourselves in station, who have been placed under our protection rather than assigned to us as servants.

Slaves are allowed to run and take sanctuary at the statue of a god, though the laws allows a slave to be ill-treated to any extent, there are nevertheless some things which the common laws of life forbid us to do to a human being.

Who does not hate Vedius Pollio [124] more even than his own slaves did, because he used to fatten his lampreys with human blood, and ordered those who had offended him in any way to be cast into his fishpond, or rather snake-pond?

That man deserved to die a thousand deaths, both for throwing his slaves to be devoured by the lampreys which he himself meant to eat, and for keeping lampreys that he might feed them in such a fashion.

Cruel masters are pointed at with disgust in all parts of the city, and are hated and loathed; the wrongdoings of kings are enacted on a wider theatre: their shame and unpopularity endures for ages: yet how far better it would have been never to have been born than to be numbered among those who have been born to do their country harm!