“Seldom, if ever, do I pause to answer criticism of my work and ideas.” But when a group of white Alabama clergymen declared him an outside agitator whose efforts were “unwise and untimely,” Martin Luther King, Jr. decided to respond. He began writing his rejoinder on the margins of a newspaper. He concluded it on the notepad of his attorney. It was smuggled out while King was behind bars following his thirteenth arrest. And “Letter from Birmingham Jail” became one of the most important documents in U.S. history.

Published in The Atlantic under the headline “The Negro Is Your Brother” in August 1963—four months after King composed his nearly 7,000-word letter—it is a classic of prison literature, of protest literature, and of civil disobedience. It also ranks among the greatest religious epistles since the first century A.D. 

This letter, like all of King’s greatest works, cannot be understood apart from his Christian faith. Faith shaped his views on just and unjust laws, on love and hate, on liberation and oppression, on human dignity and nonviolent civil disobedience. “I am grateful to God that, through the influence of the Negro church, the way of nonviolence became an integral part of our struggle,” he wrote. 

America’s Moses, its great prophet, wept over the laxity of the church and reminded it of its high calling—not to be the master or the servant of the state but rather its conscience. He died at the age of thirty-nine, an imperfect man, a dreamer who had been to the mountaintop, a martyr who bent America toward justice.