Sahih Bukhari
Virtues and Merits of the Prophet (pbuh) and his Companions
Volume: 004 / Book Number: 056 / Hadith Number: 790
Narrated 'Umar bin Taghlib:
I heard Allah's Apostle saying, "Near the Hour you will fight with people who will wear hairy shoes; and you will also fight people with flat faces like shields."