Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.044A.

Ash-Shafi’i and Sa’id bin Mansur reported from Al-Qasim that he said: “Uthman ibn ‘Affan, Zaid ibn Thabit, and Marwan ibn Al-Hakam used to cover their faces while in the state of ihram.” Taw’us said: “A person in the state of ihram may cover his face if there is dust or ashes.” Mujahid said: “If there was a sandstorm they covered their faces while in the state of ihram.”