Mukhtasar Muslim

`Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) reports that` the Messenger of Allah (peace and blessings be upon him) said: When you are three people, then two of you should not converse privately excluding the third person, until more people join you. This is because (the third person) will be grieved. (It is possible that he may become suspicious of the two.)