“What the bourgeoisie therefore produces, above all, are its own grave-diggers. Its fall and the victory of the proletariat are equally inevitable.”

Source: Fascism: What It Is and How to Fight It (1944), Ch. 5

Anarchism or Socialism (1906)

Principles of Communism (1847)
Context: Everywhere the proletariat develops in step with the bourgeoisie. In proportion, as the bourgeoisie grows in wealth, the proletariat grows in numbers. For, since the proletarians can be employed only by capital, and since capital extends only through employing labor, it follows that the growth of the proletariat proceeds at precisely the same pace as the growth of capital. Simultaneously, this process draws members of the bourgeoisie and proletarians together into the great cities where industry can be carried on most profitably, and by thus throwing great masses in one spot it gives to the proletarians a consciousness of their own strength. Moreover, the further this process advances, the more new labor-saving machines are invented, the greater is the pressure exercised by big industry on wages, which, as we have seen, sink to their minimum and therewith render the condition of the proletariat increasingly unbearable. The growing dissatisfaction of the proletariat thus joins with its rising power to prepare a proletarian social revolution.

page 300.
Manual of Political Economy

No Compromise – No Political Trading (1899)

Quoted in Doctor Goebbels: His Life and Death, Roger Manvell, Heinrich Fraenkel, New York, NY, Skyhorse Publishing, 2010 p. 25, conversation with Hertha Holk
1920s

Source: (1845), p. 112

As quoted in The Myth of the Nation and the Vision of Revolution: The Origins of Ideological Polarization in the 20th Century, Jacob Talmon, University of California Press (1981) p. 487
Undated

Problems of Leninism, August 1924 edition
The Foundations of Leninism