Musannaf Ibn Abi Shaybah 35131 — What the imam instructs governors

Abu Uthman (may Allah have mercy on him) said that Sayyiduna Umar (may Allah be pleased with him) wrote a letter to Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) and said: "Cut off the stirrups and leap onto your horses. Take off your leather socks and wear sandals. Abandon trousers and tie on waist-wrappers. Shoot at targets. Hold fast to the dress of Ma'add, and beware of the ways of the non-Arabs, for the worst of ways are the ways of the non-Arabs."