Al-Durr al-Mukhtar states: “Imitating the People of the Book (ahl al-kitab) is not disliked in every respect. They mention in this connection that Hisham said: ‘I saw Abu Yusuf wearing a pair of sandals stitched with nails. I asked, “Do you think there is any objection to this?” He replied, “No.” I said, “Sufyan and Thawr b. Yazid regarded it as disliked because it resembles the footwear of monks.” He answered, “The Messenger of Allah used to wear sandals whose uppers were covered with hair, and such sandals form part of the monks’ dress.”’” End of citation. The Prophet’s Roman jubba (cloak) appears to fall under this first category. The second category is clothing that serves as a distinctive emblem of a particular unbelieving nation, by which they are set apart from other peoples. It is impermissible for a Muslim to copy them in such dress, because that diminishes the Muslims’ visible strength and correspondingly bolsters their enemies. Modern psychology—as I have read in a number of contemporary books and magazines—confirms that outward appearance exerts an influence on the inner state, a fact that can be observed in various phenomena. The Messenger of Allah alluded to this when, while arranging the prayer-rows, he said: “Do not differ (in your rows), lest your hearts differ.” Related by Abu Dawud (1/107), al-Nasai (1/130), and Ibn Khuzayma in his Sahih, with a sound chain from al-Bara’. And from al-Nu‘man b. Bashir, in a hadith raised to the Prophet: “Servants of Allah! You must straighten your rows, or Allah will cause your faces to oppose one another.” Reported by the two Shaykhs (al-Bukhari and Muslim), the compilers of the Sunan, and others. Thus the Prophet made outward divergence a cause of inward discord. To this second type of dress applies the earlier hadith of Ibn ‘Amr, as well as his saying: “Whoever imitates a people is one of them,” recorded by Abu Dawud (2/172–173) and Ahmad (2/50) through the chain of ‘Abd al-Rahman b. Thabit.