The Rites of Hajj (Kitab Al-Manasik Wa'l-Hajj)
Dawud :: Book 10 : Hadith 1972
Narrated Abdullah ibn Abbas:
AbuMijlaz said: I asked Ibn Abbas about a thing concerning the throwing of stones at the jamrahs. He said: I do not know whether the Apostle of Allah (peace_be_upon_him) threw six or seven pebbles.