Abdullah ibn Umar
The two sides met in January 659 to discuss the selection of the new caliph. Amr supported Muawiyah, while Abu Musa preferred his son-in-law, Abdullah ibn Umar, but the latter refused to stand for election in default of unanimity. Abu Musa then proposed, and Amr agreed, to depose both Ali and Muawiyah and submit the selection of the new caliph to a Shura. In the public declaration that followed Abu Musa observed his part of the agreement, but Amr declared Ali deposed and confirmed Muawiya as caliph. This caused Abu Musa to get angry and leave the arbitration. According to Vaglieri, this was judged in later time, as a treacherous trick and disloyal act.