“It is midnight within the social order." Martin Luther King Jr. said this in a 1967 sermon called "A Knock at Midnight."
He based it on a passage from the 11th chapter of the Gospel of Luke, where Jesus asks: "Which of you who has a friend will go to him at midnight and say to him, 'Friend, lend me three loaves; for a friend of mine has arrived on a journey, and I have nothing to set before him'?"