The Messenger of Allah ﷺ said, "When you are three, two should not converse privately to the exclusion of the third, for that grieves him."
حدثنا وكيع حدثنا الأعمش عن أبي وائل
قال رسول الله ﷺ إذا كنتم ثلاثة فلا يتناجى اثنان دون واحد فإن ذلك يحزنه
Its isnad is sahih, and it is a repetition of 4093.