It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "When you are three people, then two should not converse privately excluding the third, for this will distress him."
Hadith Referenceالادب المفرد / كتاب / 1169
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : أخرجه البخاري ، كتاب الاستئذان : 6290 و مسلم : 2184 و أبوداؤد : 4851 و الترمذي : 2825 و ابن ماجه : 3775»
Abu Salih says that Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates, and he relates from the Prophet (peace and blessings be upon him) a narration similar to this. Abu Salih says: We asked, "What if there are four?" He replied: "Then there is no harm."
Hadith Referenceالادب المفرد / كتاب / 1170
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : أخرجه أبوداؤد ، كتاب الأدب : 4852 - أنظر الصحيحة : 1402»
It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "If there are three people, then two of them should not converse privately excluding the third until they join other people, because that will make the third person sad."
It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that when there are four people, then there is no harm if two of them converse separately.