(4) باب الإحرام وما يتعلق به
Ibn 'Umar (RAA) narrated, 'The Messenger of Allah (ﷺ) was asked about what the person who is in a state of Ihram (Muhrim) should wear. He answered, "A person in the state of Ihram. is not allowed to wear a sewn shirt, a turban, trousers, a hooded robe, shoes or sewn slippers (Khuff), unless one is unable to find unsown slippers, then he may wear his Khuff or shoes provided one cuts them below the ankles, and you must not wear clothing that has been dyed with sweet smelling fragrance (such as saffron)." Agreed upon, and the wording is from Muslim.
Reference: Bulugh al-Maram 731
In-book reference: Book 6, Hadith 24
English translation: Book 6, Hadith 750