Abu Dawud Book 27, Hadith Number 4045.
Chapter : Wearing a garment of silk for some excuse.
Narated By N/A : Anas said: The Apostle of Allah (peace be upon him) gave license to ‘Abd al-Rahman b. Al-Awf and al-Zubair b. al-Awwam to wear silk shirts during journey because of an itch which they had.