Musnad Ahmad 26:105

Yahya narrated to us, from Sufyan, my father narrated to me, from Abu Ya'la, from Rabi' ibn Khuthaym, from Abdullah ibn Mas'ud, from the Prophet (peace and blessings of Allah be upon him): That he drew a square line, and he drew a line in the middle of the square line, and lines to the side of the line that was in the middle of the square line, and a line outside of the square line. He said: "Do you know what this is?" They said: "Allah and His Messenger know best." He said: "This is the human being. The middle line is him, and these lines that are to his side are the afflictions that gnaw at him from every place; if this one misses him, that one strikes him. The square line is the lifespan that encompasses him, and the line outside is the hope."