“The darkness of racial injustice will be dispelled only by the light of forgiving love.”
1950s, Loving Your Enemies (Christmas 1957)
Context: The darkness of racial injustice will be dispelled only by the light of forgiving love. For more that three centuries American Negroes have been frustrated by day and bewilderment by night by unbearable injustice, and burdened with the ugly weight of discrimination. Forced to live with these shameful conditions, we are tempted to become bitter and retaliate with a corresponding hate. But if this happens, the new order we seek will be little more than a duplicate of the old order. We must in strength and humility meet hate with love.
Help us to complete the source, original and additional information
Martin Luther King, Jr. 658
American clergyman, activist, and leader in the American Ci… 1929–1968Related quotes

The Notebooks of Leonardo da Vinci (1883), X Studies and Sketches for Pictures and Decorations
LDS General Conference (October 1964)
Context: The rising sun can dispel the darkness of night, but it cannot banish the blackness of malice, hatred, bigotry, and selfishness from the hearts of humanity. Happiness and peace will come to earth only as the light of love and human compassion enter the souls of men.
It was for this purpose that Christ, the Son of righteousness, 'with healing in his wings,' came in the Meridian of Time. Through him wickedness shall be overcome, hatred, enmity, strife, poverty, and war abolished. This will be accomplished only by a slow but never-failing process of changing men's mental and spiritual attitude. The ways and habits of the world depend upon the thoughts and soul-convictions of men and women. If, therefore, we would change the world, we must first change people's thoughts. Only to the extent that men desire peace and brotherhood can the world be made better. No peace even though temporarily obtained, will be permanent, whether to individuals or nations, unless it is built upon the solid foundation of eternal principles.

'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
Source: A Testament of Hope: The Essential Writings and Speeches
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.
Interview while promoting Capitalism : A Love Story (March 2010) http://www.youtube.com/watch?v=cx2tJg91hsU
2010

This quotation, often attributed on the Internet to Plato, cannot be found in any of Plato's writings, nor can it be found in any published work anywhere until recent years. If it really were a quotation by Plato, then some author in the recorded literature of the last several centuries would have mentioned that quote, but they did not. The sentiment isn't new, however. The ancient Roman Seneca, in his work on "Morals," quoted an earlier Roman writer, Lucretius (who wrote about the year 50 B.C.), as saying "we are as much afraid in the light as children in the dark." (Seneca was paraphrasing a longer passage by Lucretius from De Rerum Natura (On the Nature of Things), Book II, lines 56 et seq.)
Misattributed

“For as children tremble and fear everything in the blind darkness, so we in the light sometimes fear what is no more to be feared than the things that children in the dark hold in terror and imagine will come true. This terror, therefore, and darkness of mind must be dispelled not by the rays of the sun and glittering shafts of daylight, but by the aspect and law of nature.”
Nam veluti pueri trepidant atque omnia caecis
in tenebris metuunt, sic nos in luce timemus
interdum, nilo quae sunt metuenda magis quam
quae pueri in tenebris pavitant finguntque futura.
hunc igitur terrorem animi tenebrasque necessest
non radii solis neque lucida tela diei
discutiant sed naturae species ratioque.
Book II, lines 55–61 (tr. Rouse)
De Rerum Natura (On the Nature of Things)

“People, beware of injustice, for injustice shall be darkness on the Day of Judgment.”
Narrated in Mosnad Ahmad, #5798, and Saheeh Al-Bukhari, #2447.
Sunni Hadith