He saw Umm Kulthum, the daughter of the Messenger of Allah ﷺ, wearing a striped silk garment called a siyara. He explained that siyara refers to a fabric ribbed with silk.
حدثنا عمرو بن عثمان وكثير بن عبيد الحمصيان قالا حدثنا بقية عن الزبيدي عن الزهري
أنه رأى على أم كلثوم بنت رسول الله ﷺ بردا سيراء قال والسيراء المضلع بالقز
[Sahih] Reported by Nasai, Adornment, chapter on the mention of the permission granted to women to wear silk brocade, no. 5299, from Amr bin Uthman with this wording. Ibn Hajar said, "It is sahih and well-known from Zubaydi" Taghliq Taliq 5/63. Bukhari also narrated it, no. 5842, through Zuhri with this wording, in abridged form.