When the happiness or misery of others depends in any respect upon our conduct, we dare not, as self-love might suggest to us, prefer the interest of one to that of many.
 Adam Smith, The Theory of Moral Sentiments (1759). copy citation

Context

“It is a stronger love, a more powerful affection, which generally takes place upon such occasions; the love of what is honourable and noble, of the grandeur, and dignity, and superiority of our own characters. 4 When the happiness or misery of others depends in any respect upon our conduct, we dare not, as self-love might suggest to us, prefer the interest of one to that of many. The man within immediately calls to us, that we value ourselves too much and other people too little, and that, by doing so, we render ourselves the proper object of the contempt and indignation of our brethren.5 Neither is this sentiment confined to men of extraordinary magnanimity and virtue.” source