Abdullah bin Masud reported,

The Prophet ﷺ said, "When you are three, two should not converse privately to the exclusion of the other until you mix with other people, for that would sadden him."

Bukhari 6290

Sahih

حدثنا عثمان حدثنا جرير عن منصور عن أبي وائل

عن عبد الله رضي الله عنه قال

النبي ﷺ إذا كنتم ثلاثة فلا يتناجى رجلان دون الآخر حتى تختلطوا بالناس أجل أن يحزنه

البخاري 6290صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Permission to enter
Chapter
If they are more than three, there is no harm in private conversation and whispering
Numbering
Darussalam 6290
Bukhari 6290