The Wealth of Nations by Part 4 Chapter 9 Page 23

the greater will be the competition in all the different trades which compose it, and the cheaper will the other two classes be supplied, both with foreign goods and with the manufactured produce of their own country.

It can never be the interest of the unproductive class to oppress the other two classes. It is the surplus produce of the land, or what remains after deducting the maintenance, first, of the cultivators, and afterwards of the proprietors, that maintains and employs the unproductive class. The greater this surplus the greater must likewise be the maintenance and employment of that class.

The establishment of perfect justice, of perfect liberty, and of perfect equality is the very simple secret which most effectually secures the highest degree of prosperity to all the three classes.