Or, in his own words from his magnum opus, The Wealth of Nations, “It is not from the benevolence of the butcher, the brewer or the baker, that we expect our dinner, but from their regard to their own interest.” Translated to the financial sector, this means: it is not to the loving kindness of banks that we owe our mortgage, but to their desire for profit and interest.
And that is as it should be. Systems which are based on selflessness fail because people are not selfless. Any stable economic system needs to take due account of the fact that people think of themselves first. This is overstating things somewhat. By which I mean that this view requires some qualification.