It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he performed two rak'ahs of 'Isha prayer with the Noble Prophet (peace and blessings of Allah be upon him) at Mina, and he also performed two rak'ahs with Sayyiduna Abu Bakr (may Allah be pleased with him) and Umar (may Allah be pleased with him), and in the early days of the caliphate of Sayyiduna Uthman (may Allah be pleased with him), he performed two rak'ahs with him as well. Later, Sayyiduna Uthman (may Allah be pleased with him) started completing the prayer (i.e., performing four rak'ahs).