Musnad Ahmad 33:1128

Musa ibn Dawud narrated to us, Ibn Lahi'ah narrated to us, from Abu al-Zubayr, from Jabir, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The likeness of the believer is like the stalk of grain; sometimes it stands straight, and sometimes it leans and becomes upright. And the likeness of the disbeliever is like the cedar tree; it remains straight, and it is not felt until it falls."