Abu Mijlaz says: I asked Sayyiduna Ibn Abbas (may Allah be pleased with them both) about something concerning the pebbles (the stoning of the Jamarat), and he said: "I do not know whether the Messenger of Allah (peace and blessings be upon him) threw six pebbles or seven."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12850