When there are three (persons), two should not converse secretly between themselves to the exclusion of the (third) one.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا كَانَ ثَلاَثَةٌ فَلاَ يَتَنَاجَى اثْنَانِ دُونَ وَاحِدٍ  

This hadith has been reported on the authority of lbn 'Umar through two different chains of transmitters.  

عَنِ النَّبِيِّ ﷺ بِمَعْنَى حَدِيثِ مَالِكٍ  

If you are three, two amongst you should not converse secretly between yourselves to the exclusion of the other (third one), unti some other people join him (and dispel his loneliness), for it may hurt his feelings.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كُنْتُمْ ثَلاَثَةً فَلاَ يَتَنَاجَى اثْنَانِ دُونَ الآخَرِ حَتَّى تَخْتَلِطُوا بِالنَّاسِ مِنْ أَجْلِ أَنْ يُحْزِنَهُ  

If you are three, two should not converse secretly to the exclusion of your companion for that hurts his feelings.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كُنْتُمْ ثَلاَثَةً فَلاَ يَتَنَاجَى اثْنَانِ دُونَ صَاحِبِهِمَا فَإِنَّ ذَلِكَ يُحْزِنُهُ  

This hadith has been reported on the authority of A'mash with the same chain of transmitters.  

عَنِ الأَعْمَشِ بِهَذَا الإِسْنَادِ