Updated: Dec 2, 2020
What a line. It's from the greek tragedy "Agamemnon", which is the first part of the trilogy The Oresteia by Aeschylus (a play about the mythical origins of democracy in Athens).
The great thing about classic literature is that it scratches an itch you never knew you had. The ideas and principles that the ancients struggled with through their epic poems help us put flesh on ideas and principles that are not yet fully formed in our own minds. We have a sense of these thoughts in our minds as we observe reality and experience life, but perhaps they have not yet crystallized. Works like The Oresteia give flesh to those thoughts because when you read a line like the one above, you say, "Somehow that is true. Grace does come somehow violent." Such is the weird way of reality: through the violent and the painful, goodness comes; out of the darkness, light shines.
The Oresteia is a rite of passage from savagery to civilization. - Robert Fagles