The Rites of Hajj (Kitab Al-Manasik Wa'l-Hajj)
Dawud :: Book 10 : Hadith 1962
Narrated Umm Jandab al-Azdiyyah:
I saw the Apostle of Allah (peace_be_upon_him) near the Jamrat al-Aqabah (the third or last pillar) riding (on a camel) and I saw a pebble between his fingers. He threw the pebbles and the people also threw (stones at the Jamrah).