Musnad Ahmad 27:451

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from Salim, from Ibn 'Umar, that a man called out and said: "O Messenger of Allah, what clothing should the *muhrim* (one in the state of ihram) avoid?" He said: "He shall not wear trousers, nor a shirt, nor a hooded cloak (*burnus*), nor a turban, nor a garment touched by saffron or *wars* (a yellow dye). Let one of you enter into ihram wearing an *izar* (waist wrapper), a *rida'* (upper garment), and two sandals. If he does not find two sandals, let him wear two leather socks (*khuffayn*), and let him cut them so that they are below the ankles."