From Sahih Bukhari (Hadith 5805):
Narrated `Abdullah:A man got up and said, O Allah's Messenger (ﷺ)! What do you order us to wear when we assume the state of Ihram?" The Prophet (ﷺ) replied, "Do not wear shirts, trousers, turbans, hooded cloaks or Khuffs (socks made from thick fabric or leather), but if a man has no sandals, he can wear Khuffs after cutting them short below the ankles; and do not wear clothes touched with (perfumes) of saffron or wars
Reference: Bukhari 5805