Sahih Muslim
The Book Pertaining to Clothes and Decoration (Kitab Al-Libas wal-Zinah)
Book Number: 024 / Hadith Number: 5168
Anas b. Malik reported to them (his companions) that Allah's Messnger (may peace be upon him) had granted concession to Abd al-Rahman b. *Anf and Zubair b. 'Awwam for the wearing of a silk shirt during the journey and because of itch which they both had or any other disease from which both of them had been suffering.