Starets Zosima, from Fyodor Dostoyevsky’s 
The Brothers Karamazov:
At some thoughts one stands perplexed, above all at the sight of human sin, and wonders whether to combat it by force or by humble love. Always decide ‘I will combat it by humble love.’ If you resolve on that once and for all, you can conquer the whole world. Loving humility is a terrible force: it is the strongest of all things, and there is nothing else like it.