Dorian Gray by Oscar Wilde Chapter 7 Page 25

Finally, he came back, went over to the picture, and examined it. In the dim arrested light that struggled through the cream-coloured silk blinds, the face appeared to him to be a little changed. The expression looked different. One would have said that there was a touch of cruelty in the mouth. It was certainly strange.

He turned round and, walking to the window, drew up the blind. The bright dawn flooded the room and swept the fantastic shadows into dusky corners, where they lay shuddering. But the strange expression that he had noticed in the face of the portrait seemed to linger there, to be more intensified even. The quivering ardent sunlight showed him the lines of cruelty round the mouth as clearly as if he had been looking into a mirror after he had done some dreadful thing.