Sahih al-Bukhari 6356
صحيح البخاري#6356Sahihحَدَّثَنَا أَبُو الْيَمَانِ، أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي عَبْدُ اللَّهُ بْنُ ثَعْلَبَةَ بْنِ صُعَيْرٍ ـ وَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم قَدْ مَسَحَ عَنْهُ ـ أَنَّهُ رَأَى سَعْدَ بْنَ أَبِي وَقَّاصٍ يُوتِرُ بِرَكْعَةٍ.
Narrated `Abdullah bin Tha`laba bin Su'air:whose eye Allah's Messenger (ﷺ) had touched, that he had seen Sa`d bin Abi Waqqas offering one rak`a only for the witr prayer
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 80:53