Sayyiduna Samurah bin Jundub (may Allah be pleased with him) states that the Prophet (peace and blessings be upon him) forbade that, when there are three people, two of them talk privately, leaving out the third.
Al-Tabarani and al-Bazzar recorded it; al-Tabarani's chain contains a narrator whom I do not know, and al-Bazzar's chain contains Yusuf bin Khalid al-Samti, who is matruk (abandoned).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 12951
Hadith Gradingمحدثین:ضعیف جداً
Hadith Takhrij«اخرجه البزار فى المسند (2057) اخرجه الطبراني فى المعجم الكبير (7070)»