To say 'Allahu Akbar' on throwing every pebble

Narrated Al-A`mash: I heard Al-Hajjaj saying on the pulpit, "The Sura in which Al-Baqara (the cow) is mentioned and the Sura in which the family of `Imran is mentioned and the Sura in which the women (An-Nisa) is mentioned." I mentioned this to Ibrahim, and he said, `Abdur-Rahman bin Yazid told me, 'I was with Ibn Mas`ud, when he did the Rami of the Jamrat-ul-Aqaba. He went down the middle of the valley, and when he came near the tree (which was near the Jamra) he stood opposite to it and threw seven small pebbles and said: 'Allahu-Akbar' on throwing every pebble.' Then he said, 'By Him, except Whom none has the right to be worshipped, here (at this place) stood the one on whom Surat-al-Baqra was revealed (i.e. Allah's Messenger (ﷺ)).' "