“My mission is to suffer for all those who suffer without knowing it. I must pay for them, expiate their unconsciousness, their luck to be ignorant of how unhappy they are.”

Source: White Oleander

A Personal Matter (1964)

Nahj al-Balagha

Source: Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen

"Buddhism and the Coming Revolution" (1961, 1969)

Nobel acceptance speech (1989)
Context: I believe all suffering is caused by ignorance. People inflict pain on others in the selfish pursuit of their happiness or satisfaction. Yet true happiness comes from a sense of inner peace and contentment, which in turn must be achieved through the cultivation of altruism, of love and compassion and elimination of ignorance, selfishness and greed.
The problems we face today, violent conflicts, destruction of nature, poverty, hunger, and so on, are human-created problems which can be resolved through human effort, understanding and the development of a sense of brotherhood and sisterhood. We need to cultivate a universal responsibility for one another and the planet we share. Although I have found my own Buddhist religion helpful in generating love and compassion, even for those we consider our enemies, I am convinced that everyone can develop a good heart and a sense of universal responsibility with or without religion.

Source: Lovingkindness: The Revolutionary Art of Happiness

Source Book in Ancient Philosophy (1907), The Golden Sayings of Democritus