The Wealth of Nations by Part 1 Chapter 6 Page 7

this labour of inspection and direction. Though in settling them some regard is had commonly, not only to his labour and skill, but to the trust which is reposed in him, yet they never bear any regular proportion to the capital of which he oversees the management; and the owner of this capital, though he is thus discharged of almost all labour, still expects that his profits should bear a regular proportion to his capital. In the price of commodities, therefore, the profits of stock constitute a component part altmust be due for the profits of the stock which advanced the wages and furnished the materials of that labour.

As soon as the land of any country has all become private property, the landlords, like all other men, love to reap where they never sowed, and demand a rent even for its natural produce.