[18] Again, he who, when requested to requite a favour, contradicts the man who says that he ought to consider himself a debtor, is disobedient; but he who, in addition to making no return, is so carried away by contentiousness that he endeavours to do the person what harm he can, commits unredeemable wickedness. And further, he who never approaches, nor practises sacrifices, or any of the other observances required by piety, disobeys the commandments which the law usually ordains in such matters; but he who resists and turns aside to the opposite disposition, impiety, is a wicked man and a minister of impiety.