'Abdullah reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "When there are three people, two should not converse together to the exclusion of the third."  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ إِذَا كَانُوا ثَلاَثَةً فَلاَ يَتَنَاجَى اثْنَانِ دُونَ الثَّالِثِ