Sayyidina Abdullah (RA) reported that Allah’s Messenger (SAW) said, “When you are three people, two should not engage in a private conversation keeping their companion apart.” Sufyan in his hadith uses the words, “The two must not whisper at the exclusion of the third,’ adding that it grieves him.
[Ahmed 3560, Bukhari 6290, Muslim 2184, Abu Dawud 4851, Ibn e Majah 3775]