Maliks Muwatta Book 20, Hadith Number 13A.
Section : Veiling the Face while in Ihram.
Yahya related to me from Malik from Yahya ibn Said that al-Qasim ibn Muhammad said that al-Furafisa ibn Umayr al-Hanafi saw Uthman ibn Affan at al-Arj, and he was covering his face while in ihram.