Sahih Bukhari Volume 001, Book 003, Hadith Number 136.
Narated By Ibn 'Umar : A man asked the Prophet : "What (kinds of clothes) should a Muhrim (a Muslim intending to perform 'Umra or Hajj) wear? He replied, "He should not wear a shirt, a turban, trousers, a head cloak or garment scented with saffron or Wars (kinds of perfumes). And if he has no slippers, then he can use Khuffs (leather socks) but the socks should be cut short so as to make the ankles bare." (See Hadith No. 615, Vol. 2).