Abdullah bin Masud reported,

The Messenger of Allah ﷺ said, "When you are three, two of you should not converse privately apart from your companion, for that saddens him."

Muslim 5698

Sahih

و حدثناه إسحق بن إبراهيم أخبرنا عيسى بن يونس ح و حدثنا ابن أبي عمر حدثنا سفيان كلاهما عن الأعمش بهذا الإسناد

مسلم 5698صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Peace
Chapter
Prohibition of two people conversing privately without the third when he is not pleased
Numbering
Darussalam 5698
Muslim 5698