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."
قَالَ النَّبِيُّ ﷺ {إِذَا كُنْتُمْ ثَلاَثَةً فَلاَ يَتَنَاجَى رَجُلاَنِ دُونَ الآخَرِ حَتَّى تَخْتَلِطُوا بِالنَّاسِ أَجْلَ أَنْ يُحْزِنَهُ}
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
"When you are three, two should not converse (privately) to the exclusion of their companion, because that makes him sad." (Using translation from Ibn Mājah 3775)
عَنْ رَسُولِ اللَّهِ ﷺ قَالَ «إِذَا كُنْتُمْ ثَلَاثَةً فَلَا يَتَنَاجَى اثْنَانِ دُونَ صَاحِبِهِمَا حَتَّى يَخْتَلِطُوا بِالنَّاسِ فَإِنَّ ذَلِكَ يُحْزِنُهُ»
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." (Using translation from Bukhārī 6290)
"إذَا كُنْتُمْ ثلاثةً فلا يتناجَى رجلانِ دونَ الآخر، حتَّى تختلطوا بالنَّاسِ، فإِنَّ ذلك يَحْزُنُه" .