(47) باب إِذَا كَانُوا أَكْثَرَ مِنْ ثَلاَثَةٍ فَلاَ بَأْسَ بِالْمُسَارَّةِ وَالْمُنَاجَاةِ
Narrated `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."
Reference: Sahih al-Bukhari 6290
In-book reference: Book 79, Hadith 62
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 74, Hadith 305