Mukhtasar Bukhari (Abridged) 2066 — If more than three are present

Narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Noble Prophet (peace and blessings of Allah be upon him) said: "When you are three people in one place, then two of you should not whisper to each other excluding the third, until there are more people, so that (the third) does not feel distressed."