“Upheaval after upheaval has reminded up that modern man is traveling along the road called hate, in a journey that will bring us to destruction and damnation. Far from being the pious injunction of a Utopian dreamer, the command to love one's enemy is an absolute necessity for our survival. Love even for enemies is the key to the solution of the problems of our world.”

Source: The Hiding Place: The Triumphant True Story of Corrie Ten Boom

1950s, Loving Your Enemies (Christmas 1957)

1950s, What Desires Are Politically Important? (1950)
Context: We love those who hate our enemies, and if we had no enemies there would be very few people whom we should love.
All this, however, is only true so long as we are concerned solely with attitudes towards other human beings. You might regard the soil as your enemy because it yields reluctantly a niggardly subsistence. You might regard Mother Nature in general as your enemy, and envisage human life as a struggle to get the better of Mother Nature. If men viewed life in this way, cooperation of the whole human race would become easy. And men could easily be brought to view life in this way if schools, newspapers, and politicians devoted themselves to this end. But schools are out to teach patriotism; newspapers are out to stir up excitement; and politicians are out to get re-elected. None of the three, therefore, can do anything towards saving the human race from reciprocal suicide.

2011, Address on the natural and nuclear energy disasters in Japan (March 2011)
Context: In the midst of economic recovery and global upheaval, disasters like this remind us of the common humanity that we share. We see it in the responders who are risking their lives at Fukushima. We show it through the help that has poured into Japan from 70 countries. And we hear it in the cries of a child, miraculously pulled from the rubble.
In the coming days, we will continue to do everything we can to ensure the safety of American citizens and the security of our sources of energy. And we will stand with the people of Japan as they contain this crisis, recover from this hardship, and rebuild their great nation.

1960s, A Time for Choosing (1964)

Vol. I [Bernhard Tauchnitz, 1860] ( p. 194 https://books.google.com/books?id=wUN2KP79lhUC&pg=PA194)
Also in The Cambridge Companion to Sensation Fiction edited by Andrew Mangham [Cambridge University Press, 2013, ISBN 1-107-51169-0] ( p. 82 https://books.google.com/books?id=rQZCAQAAQBAJ&pg=PA82)
The King of Inventors: A Life of Wilkie Collins by Catherine Peters [Princeton University Press, 2014, ISBN 1-400-86345-7] ( p. 224 https://books.google.com/books?id=T0AABAAAQBAJ&pg=PA224)
Cemetery of the Murdered Daughters: Feminism, History, and Ingeborg Bachmann by Sara Lennox [University of Massachusetts Press, 2006, ISBN 1-558-49552-5] ( p. 227 https://books.google.com/books?id=_9VjDtk5ss4C&pg=PA227)
The Law and the Lady (1875)