Sahih al-Bukhari 2550
صحيح البخاري#2550Sahihحَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، حَدَّثَنِي نَافِعٌ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا نَصَحَ الْعَبْدُ سَيِّدَهُ، وَأَحْسَنَ عِبَادَةَ رَبِّهِ، كَانَ لَهُ أَجْرُهُ مَرَّتَيْنِ ".
Narrated `Abdullah:The Prophet (ﷺ) said, "If a slave serves his Saiyid (i.e. master) sincerely and worships his Lord (Allah) perfectly, he will get a double reward
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: 49:33