Sunan Ibn Majah, Chapter: The Chapters on Ascetism (Zuhd)

that the Prophet (saw) drew a square, and a line in the middle of the square, and lines to the side of the line in the middle of the square, and a line outside the square, and he said: "Do you know what this is?" They said: "Allah and His Messenger know best." He said: "Man is the line in the middle, and these lines to his side are the sicknesses and problems that assail him from all places. If one misses him, another will befall him. The square is his life span, at his neck; and the line outside it is (his) hope."