Sahih al-Bukhari, Volume 5, Book 57, Hadith 72 (USC-MSA) ⓘ
Narrated Sa`d: No doubt, (for some time) I stood for one-third of the Muslims.
حَدَّثَنَا مَكِّيُّ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هَاشِمُ بْنُ هَاشِمٍ، عَنْ عَامِرِ بْنِ سَعْدٍ، عَنْ أَبِيهِ، قَالَ لَقَدْ رَأَيْتُنِي وَأَنَا ثُلُثُ الإِسْلاَمِ،.
also referenced under: Book 62, Hadith 74 (In-Book) & Hadith 3726 (DarusSalam)