Musnad Ahmad 31:776

Abu Nu'aym narrated to us, al-Walid—meaning Ibn 'Abd Allah ibn Jumay'—narrated to us, he said: Abu Salamah informed me, from Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) came to Ibn Sayyad while he was playing with the boys. He said: "Do you bear witness that I am the Messenger of Allah?" He (Ibn Sayyad) said: "Do you bear witness that I am the Messenger of Allah?" The Messenger of Allah (peace and blessings of Allah be upon him) said: "I have hidden a secret for you." He said: "Dukh (smoke)." He said: "Be driven away, for you will never exceed your limit."