in his letter to Malik al-Ashtar when he appointed him governor of Egypt; said, 'Thereafter, look into the affairs of your executives. Give them appointment after tests and do not appoint them according to partiality or favouritism, because these two things constitute the sources of injustice and unfairness. Select from among them those who are people of experience and modesty, hailing from virtuous houses, having preceded in [embracing] Islam.'