From Sahih Bukhari (Hadith 5849):
Narrated Al-Bara:The Prophet (ﷺ) ordered us to observe seven things: To visit the sick; follow funeral processions; say 'May Allah bestow His Mercy on you', to the sneezer if he says, 'Praise be to Allah!; He forbade us to wear silk, Dibaj, Qassiy and Istibarq (various kinds of silken clothes); or to use red Mayathir (silkcushions). (See Hadith No. 253 A, Vol)
Reference: Bukhari 5849