“Die then. This is my cure for sore knees.”

Prefiero morir de pie que vivir de rodillas.
As quoted in Liberation Theologies in North America and Europe‎ (1979) by Gerald H. Anderson and Thomas F. Stransky, p. 281; this is sometimes misattributed to the more modern revolutionary, Che Guevara, and to "La Pasionaria" Dolores Ibárruri, especially in Spain, where she popularized it in her famous speeches during the Spanish Civil War, to José Martí, and to Aeschylus who is credited with a similar declaration in Prometheus Bound: "For it would be better to die once and for all than to suffer pain for all one's life." The phrase "better that we should die on our feet rather than live on our knees" was spoken by François-Noël Gracchus Babeuf in his defence of the Conspiracy of Equals in April 1797. In French it read, 'Ne vaut-il pas mieux emporter la gloire de n'avoir pas survecu a la servitude?' but translated this bears no resemblance whatever to the quote under discussion. see: The Defense of Gracchus Babeuf Before the High Court of Vendome (1967), edited and translated by John Anthony Scott, p. 88 and p. 90, n. 12.
Spanish variants:
¡Prefiero morir de pie que vivir siempre arrodillado!
I'd prefer to die standing, than to live always on my knees.
As quoted in Operación Cobra : historia de una gesta romántica (1988) by Alvaro Pablo Ortiz and Oscar Lara, p. 29
Variant translations:
Men of the South! It is better to die on your feet than to live on your knees!
With an extension, as quoted in Timeless Mexico (1944) by Hudson Strode, p. 259
I would rather die standing than live on my knees!
It is better to die on your feet than to live on your knees!
I prefer to die standing than to live forever kneeling.
Prefer death on your feet to living on your knees.

This is usually attributed to Emiliano Zapata, but sometimes to Aeschylus, who is credited with expressing similar sentiments in Prometheus Bound: "For it would be better to die once and for all than to suffer pain for all one's life".
Misattributed

Xavier Ternisien, A "Charlie Hebdo", on n'a "pas l’impression d’égorger quelqu’un avec un feutre" http://www.lemonde.fr/actualite-medias/article/2012/09/20/je-n-ai-pas-l-impression-d-egorger-quelqu-un-avec-un-feutre_1762748_3236.html, Le Monde, 20 september 2012.

Idle Thoughts of an Idle Fellow (1886)

Source: As quoted in "Net Impact: One man's cyber-crusade against Russian corruption" http://archive.is/FGqQE (4 April 2011), by Julia Ioffe, The New Yorker