Musnad Ahmad 32:1696

'Affan narrated to us, Hammam narrated to us, Qatadah narrated to us, that Anas ibn Malik informed him: "That al-Zubayr ibn al-'Awwam and 'Abd al-Rahman ibn 'Awf complained to the Messenger of Allah, peace and blessings of Allah be upon him, about lice. So he granted them a concession to wear silk shirts during a military expedition of theirs."