Sahih
Muslim
صحيح مسلم
39
The Book of Greetings
كتاب السلام
Chapter 15: The Prohibition Of Two People Conversing Privately To The Exclusion Of A Third Without His Consent
باب تَحْرِيمِ مُنَاجَاةِ الاِثْنَيْنِ دُونَ الثَّالِثِ بِغَيْرِ رِضَاهُ
Sahih Muslim 2183 a
Ibn Umar reported Allah's Messenger (ﷺ) as saying
When there are three (persons), two should not converse secretly between themselves to the exclusion of the (third) one.حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا كَانَ ثَلاَثَةٌ فَلاَ يَتَنَاجَى اثْنَانِ دُونَ وَاحِدٍ " .
Grade: Sahih