“Returning violence for violence multiplies violence, adding deeper darkness to a night already devoid of stars… Hate cannot drive out hate: only love can do that.”

Source: The Ways and Power of Love (1954), p. xi

1960s, Where Do We Go from Here: Chaos or Community? (1967)
Context: I say to you today that I still stand by nonviolence. And I am still convinced that it is the most potent weapon available to the Negro in his struggle for justice in this country. And the other thing is that I am concerned about a better world. I'm concerned about justice. I'm concerned about brotherhood. I'm concerned about truth. And when one is concerned about these, he can never advocate violence. For through violence you may murder a murderer but you can't murder murder. Through violence you may murder a liar but you can't establish truth. Through violence you may murder a hater, but you can't murder hate. Darkness cannot put out darkness. Only light can do that.

'Where Do We Go From Here?" as published in Where Do We Go from Here : Chaos or Community? (1967), p. 62; many statements in this book, or slight variants of them, were also part of his address Where Do We Go From Here?" which has a section below. A common variant appearing at least as early as 1968 has "Returning violence for violence multiplies violence..." An early version of the speech as published in A Martin Luther King Treasury (1964), p. 173, has : "Returning hate for hate multiplies hate..."
1960s
Context: The ultimate weakness of violence is that it is a descending spiral, begetting the very thing it seeks to destroy. Instead of diminishing evil, it multiplies it. Through violence you may murder the liar, but you cannot murder the lie, nor establish the truth. Through violence you may murder the hater, but you do not murder hate. In fact, violence merely increases hate. So it goes. … Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that.

Utopia and Violence (1947)
Context: Not only do I hate violence, but I firmly believe that the fight against it is not hopeless. I realize that the task is difficult. I realize that, only too often in the course of history, it has happened that what appeared at first to be a great success in the fight against violence was followed by a defeat. I do not overlook the fact that the new age of violence which was opened by the two World wars is by no means at an end. Nazism and Fascism are thoroughly beaten, but I must admit that their defeat does not mean that barbarism and brutality have been defeated. On the contrary, it is no use closing our eyes to the fact that these hateful ideas achieved something like a victory in defeat. I have to admit that Hitler succeeded in degrading the moral standards of our Western world, and that in the world of today there is more violence and brutal force than would have been tolerated even in the decade after the first World war. And we must face the possibility that our civilization may ultimately be destroyed by those new weapons which Hitlerism wished upon us, perhaps even within the first decade after the second World war; for no doubt the spirit of Hitlerism won its greatest victory over us when, after its defeat, we used the weapons which the threat of Nazism had induced us to develop.

Source: Kinski Uncut : The Autobiography of Klaus Kinski (1996), p. 2

Helen Burns to Jane (Ch. 6)
Jane Eyre (1847)
Context: It is not violence that best overcomes hate — nor vengeance that most certainly heals injury. … Read the New Testament, and observe what Christ says, and how he acts — make his word your rule, and his conduct your example. … Love your enemies; bless them that curse you; do good to them that hate you and despitefully use you.

1960s, Freedom From The Known (1969)
Context: We human beings are what we have been for millions of years — colossally greedy, envious, aggressive, jealous, anxious and despairing, with occasional flashes of joy and affection. We are a strange mixture of hate, fear and gentleness; we are both violence and peace.