Musnad Ahmad 33:1037

Hassan narrated to us, Ibn Lahi'ah narrated to us, Abu al-Zubayr narrated to us, from Jabir, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The likeness of the believer is like the stalk of grain; it stands straight at one time, and it falls at another time. And the likeness of the disbeliever is like the cedar tree; it remains standing straight until it falls, and it does not perceive."