(24) The Book of Hajj
كتاب مناسك الحج
(227) Chapter: The Number of Pebbles To bE Thrown At the Jimar.
(227) باب عَدَدِ الْحَصَى الَّتِي يُرْمَى بِهَا الْجِمَارُ
Sunan an-Nasa'i 3077 
Sad said:
"We returned during the Hajj with the Prophet and some of us said that they had stoned (the Jamarat) with seven stones, and other said that they had done so with six, and no one denounced anyone else."
أَخْبَرَنِي يَحْيَى بْنُ مُوسَى الْبَلْخِيُّ، قَالَ حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنِ ابْنِ أَبِي نَجِيحٍ، قَالَ قَالَ مُجَاهِدٌ قَالَ سَعْدٌ رَجَعْنَا فِي الْحَجَّةِ مَعَ النَّبِيِّ صلى الله عليه وسلم وَبَعْضُنَا يَقُولُ رَمَيْتُ بِسَبْعِ حَصَيَاتٍ وَبَعْضُنَا يَقُولُ رَمَيْتُ بِسِتٍّ فَلَمْ يَعِبْ بَعْضُهُمْ عَلَى بَعْضٍ ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan an-Nasa'i 3077
In-book reference : Book 24, Hadith 460
English translation : Vol. 3, Book 24, Hadith 3079