Sahih al-Bukhari 1984
صحيح البخاري#1984SahihNarrated Muhammad bin `Abbas:I asked Jabir "Did the Prophet (ﷺ) forbid fasting on Fridays?" He replied, "Yes." (Other narrators added, "If he intends to fast only that day)
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: 30:91