Musannaf Ibn Abi Shayba 28:80

Muhammad ibn Mus’ab narrated to us, from al-Awza’i, from al-Walid ibn Hisham, who said: I wrote to Ibn Muhayriz asking him about wearing silk and *yalamiq* (outer garments/cloaks) in the Abode of War (*Dar al-Harb*). He said: So he wrote back, "If you are at your most intense in detesting what is disliked at the time of fighting, when you are exposing yourself to martyrdom [then it is permissible]."