Sahih Muslim Book 7, Hadith Number 2970.

Chapter : Stoning at Jamrat al-‘Aqaba from the heart of the valley in the state that Mecca is on the left side and pronouncing of takbir while throwing every pebble.

‘Abd al-Rahman b. Yazid reported that ‘Abdullah b. Mas’ud (Allah be pleased with them) threw seven pebbles at Jamrat al-‘Aqaba from the heart of the valley. He pronounced Takbir with every pebble. It was said to him that people fling stones from the upper side (of the valley), whereupon ‘Abdullah b. Mas’ud (Allah he pleased with them) said: By him, besides Whom there is no other god, that is the place (of flinging stones) of one upon whom Surah al-Baqara was revealed (the Holy Prophet).