Prohibition of two Holding Secret Counsel to the Exclusion of Conversing together a Third
Ibn Mas'ud (May Allah be pleased with him) said: The Messenger of Allah صلى الله عليه وسلم said, "When three of you are together, two of you must not converse privately ignoring the third till the number increases, lest the third should be grieved.''
[Al-Bukhari and Muslim].
Commentary: This Hadith tells us that holding private counsel has been prohibited for the reason that it hurts the feelings of the Muslim who is ignored; and to hurt the feelings of a Muslim is a great sin indeed. Allah says: "And those who annoy believing men and women undeservedly, bear on themselves the crime of slander and plain sin.'' (33:58) Whispering of the two is permissible when all the three mix up in a crowd. Then the two can speak to each other in confidence.