It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: When you are three people, then two of you should not whisper to each other leaving the third one out. Abu Salih, the narrator, said: What if there are four people? He (Ibn Umar) said: Then this does not cause any harm (i.e., then there is no problem).