Sahih al-Bukhari 2550
صحيح البخاري#2550SahihNarrated `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
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 49:33