The Wealth of Nations by Part 4 Chapter 9 Page 20

the materials of its work and with the fund of its subsistence, with the corn and cattle which it consumes while it is employed about that work. The proprietors and cultivators finally pay both the wages of all the workmen of the unproductive class, and of the profits of all their employers. Those workmen and their employers are properly the servants of the proprietors and cultivators. They are only servants who work without doors, as menial servants work within. Both the one and the other, however, are equally maintained at the expense of the same masters.

The labour of both is equally unproductive. It adds nothing to the value of the sum total of the rude produce of the land. Instead of increasing the value of that sum total, it is a charge and expense which must be paid out of it.