Musnad Ahmad 652:9

Abu Mu'awiyah narrated to us, from al-A'mash, from al-Sha'bi, from al-Nu'man ibn Bashir, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The likeness of the believer is as the likeness of the body; if a man complains of his head, the rest of his body calls out for him."