… is from pages 191-192 of Leonard Read‘s 1956 essay “Unearned Riches,” which is chapter XIV in the 1956 collection, edited by Mary Sennholz, On Freedom and Free Enterprise: Essays in Honor of Ludwig von Mises (available for free here) (original emphasis):
Our wage earner may think of his plight as hapless when compared to the one who inherited his millions. True, the millionaire has gained much from the doings of others. But the wage earner himself owes his life to the doings of others. It is not that possessing millions and having life are alternative propositions. That is not the point. The point is that both flow from the same exchange process and that whatever each has – be it autos, houses, food, clothing, heat, millions, knowledge, or life itself – comes to him unearned in the sense that he alone did not produce all of it. We trade because we can all get more satisfaction from our labor by that means. Vast stores are available to those who have anything to trade that others value. In the free market, each earns all that he receives in willing exchange. This is fantastically more than one could produce by himself.