The just man who disdains either to take or to give any advantage, but who would think it less dishonourable to give than to take one; the man who, in all private transactions, would be the most beloved and the most esteemed; in those public transactions is regarded as a fool and an idiot, who does not understand his business
 Adam Smith, The Theory of Moral Sentiments (1759). copy citation

Context

“Treaties are violated; and the violation, if some advantage is gained by it, sheds scarce any dishonour upon the violator. The ambassador who dupes the minister of a foreign nation, is admired and applauded. The just man who disdains either to take or to give any advantage, but who would think it less dishonourable to give than to take one; the man who, in all private transactions, would be the most beloved and the most esteemed; in those public transactions is regarded as a fool and an idiot, who does not understand his business; and he incurs always the contempt, and sometimes even the detestation of his fellow-citizens. In war, not only what are called the laws of nations, are frequently violated, without bringing (among his own fellow-citizens, whose judgments he only regards)” source