Sahih al-Bukhari 6290
صحيح البخاري#6290SahihNarrated `Abdullah:The Prophet (ﷺ) said, "When you are three persons sitting together, then no two of you should hold secret counsel excluding the third person until you are with some other people too, for that would grieve him
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: 79:62