Maliks Muwatta Book 20, Hadith Number 16.
Section : Veiling the Face while in Ihram.
Yahya related to me from Malik from Hisham ibn Urwa that Fatima bint al-Mundhir said, “We used to veil our faces when we were in ihram in the company of Asma bint Abi Bakr as-Siddiq.”