كتاب الحج
15  
The Book of Pilgrimage
(50)
Chapter: Stoning Jamrat Al-'Aqabah from the bottom of the valley; Makkah should be on to one's left and one should say Takbir with each throw
(50)
باب رَمْىِ جَمْرَةِ الْعَقَبَةِ مِنْ بَطْنِ الْوَادِي وَتَكُونُ مَكَّةُ عَنْ يَسَارِهِ وَيُكَبِّرُ مَعَ كُلِّ حَصَاةٍ
Sahih Muslim 1296 a

'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).
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَأَبُو كُرَيْبٍ قَالاَ حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ يَزِيدَ، قَالَ رَمَى عَبْدُ اللَّهِ بْنُ مَسْعُودٍ جَمْرَةَ الْعَقَبَةِ مِنْ بَطْنِ الْوَادِي بِسَبْعِ حَصَيَاتٍ يُكَبِّرُ مَعَ كُلِّ حَصَاةٍ ‏.‏ قَالَ فَقِيلَ لَهُ إِنَّ أُنَاسًا يَرْمُونَهَا مِنْ فَوْقِهَا ‏.‏ فَقَالَ عَبْدُ اللَّهِ بْنُ مَسْعُودٍ هَذَا وَالَّذِي لاَ إِلَهَ غَيْرُهُ مَقَامُ الَّذِي أُنْزِلَتْ عَلَيْهِ سُورَةُ الْبَقَرَةِ.
Reference : Sahih Muslim 1296a
In-book reference : Book 15, Hadith 335
USC-MSA web (English) reference : Book 7, Hadith 2970
  (deprecated numbering scheme)