Hadith 4851
Abdullah (bin Masud) reported the Messenger of Allah ﷺ as saying: Two persons should not talk privately ignoring the third, for that will grieve him.
Hadith 4852
A similar tradition has been transmitted by Ibn Umar through a different chain of narrators. This version has: Abu Salih said: I asked Ibn Umar: If they are four? He replied: then it does not harm you.