Sahih Bukhari Volume 7, Book 72, Hadith Number 686.

Narrated By Ibn ‘Umar : A man asked, “O Allah s Apostle What kind of clothes should a Muhrim wear?” The Prophet, said, “A Muhrim should not wear a shirt, trousers a hooded cloak, or Khuffs (leather socks covering the ankles) unless he cannot get sandals, in which case he should cut the part (of the Khuff) that covers the ankles.”