“It is to labour… and to labour only, that man owes every thing possessed of exchangeable value. Labour is the talisman that has raised him from the condition of the savage — that has changed the desert and the forest into cultivated fields… Labour tho that has covered the earth with cities and the ocean with ships — of wealth that has given us plenty, comfort, and elegance, instead of want, misery, and barbarism.”

Comment of late 1788 or early 1789 upon his slaves http://www.mountvernon.org/george-washington/slavery/the-only-unavoidable-subject-of-regret/, as recorded by David Humphreys, in his notebooks on his conversations with Washington, now in the Rosenbach Library in Philadelphia<!-- as quoted in "Housing and Family Life of the Mount Vernon Negro," unpublished paper by Charles C. Wall, prepared for the Mount Vernon Ladies' Association (May 1962), prefatory note]. -->
1780s
Context: The unfortunate condition of the persons, whose labour in part I employed, has been the only unavoidable subject of regret. To make the Adults among them as easy & as comfortable in their circumstances as their actual state of ignorance & improvidence would admit; & to lay a foundation to prepare the rising generation for a destiny different from that in which they were born; afforded some satisfaction to my mind, & could not I hoped be displeasing to the justice of the Creator.

Source: The Principles of Political Economy and Taxation (1821) (Third Edition), Chapter I, Section I, On Value, p. 5

Lakshmidhar Mishra in: Human Bondage: Tracing Its Roots in India http://books.google.co.in/books?id=WNuGAwAAQBAJ&pg=PA425, SAGE Publications India, 12 July 2011, p. 425
From his book On the “Labour Problems in Indian Industry”

Source: The Principles of Political Economy and Taxation (1821) (Third Edition), Chapter XVI, Taxes on Wages, p. 141

Source: The Wealth of Nations (1776), Book I, Chapter V.
Context: Every man is rich or poor according to the degree in which he can afford to enjoy the necessaries, conveniences, and amusements of human life. But after the division of labour has once thoroughly taken place, it is but a very small part of these with which a man's own labour can supply him. The far greater part of them he must derive from the labour of other people, and he must be rich or poor according to the quantity of that labour which he can command, or which he can afford to purchase. The value of any commodity, therefore, to the person who possesses it, and who means not to use or consume it himself, but to exchange it for other commodities, is equal to the quantity of labour which it enables him to purchase or command. Labour, therefore, is the real measure of the exchangeable value of all commodities.

Notebook VII, The Chapter on Capital, pp. 628–629.
Grundrisse (1857/58)
Context: The development of fixed capital indicates in still another respect the degree of development of wealth generally, or of capital…
The creation of a large quantity of disposable time apart from necessary labour time for society generally and each of its members (i. e. room for the development of the individuals’ full productive forces, hence those of society also), this creation of not-labour time appears in the stage of capital, as of all earlier ones, as not-labour time, free time, for a few. What capital adds is that it increases the surplus labour time of the mass by all the means of art and science, because its wealth consists directly in the appropriation of surplus labour time; since value directly its purpose, not use value. It is thus, despite itself, instrumental in creating the means of social disposable time, in order to reduce labour time for the whole society to a diminishing minimum, and thus to free everyone’s time for their own development. But its tendency always, on the one side, to create disposable time, on the other, to convert it into surplus labour...
The mass of workers must themselves appropriate their own surplus labour. Once they have done so – and disposable time thereby ceases to have an antithetical existence – then, on one side, necessary labour time will be measured by the needs of the social individual, and, on the other, the development of the power of social production will grow so rapidly that, even though production is now calculated for the wealth of all, disposable time will grow for all. For real wealth is the developed productive power of all individuals. The measure of wealth is then not any longer, in any way, labour time, but rather disposable time. Labour time as the measure of value posits wealth itself as founded on poverty, and disposable time as existing in and because of the antithesis to surplus labour time; or, the positing of an individual’s entire time as labour time, and his degradation therefore to mere worker, subsumption under labour. The most developed machinery thus forces the worker to work longer than the savage does, or than he himself did with the simplest, crudest tools.

Vol. II, Ch. XXI, p. 520.
(Buch II) (1893)

Source: A Treatise On Political Economy (Fourth Edition) (1832), Book I, On Production, Chapter VII, p. 85

His first speech as Leader of the Labour Party http://www.youtube.com/watch?v=kJwOABXNdn4/ 25 Sep 2010
2010