Musnad Ahmad 33:503

Hassan ibn Musa al-Ashyab narrated to us, Ibn Lahi'ah narrated to us, Abu al-Zubayr narrated to us, from Jabir, that he said: The Messenger of Allah, may Allah bless him and grant him peace, threw the Jamrah while on his camel with pebbles of the size of a date stone, while he was saying: "Take your rites from me, for I do not know, perhaps I will not perform Hajj after this Hajj of mine."