It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "It is not permissible for a man to marry a woman on the condition of divorcing another; it is not permissible for a man to sell over the sale of his companion until he gives it up; it is not permissible for three people who are in a desolate land not to appoint one of them as their leader; and it is not permissible for three people who are in a desolate land that two of them converse privately, leaving out their third companion."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13736