Musnad Ahmad 27:887

I read to Abd al-Rahman, [from] Malik, from Abdullah ibn Dinar, from Abdullah ibn Umar, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade the *muhrim* (one in the state of ihram) from wearing a garment dyed with saffron or *wars* (a yellow plant used for dyeing). And he said: "Whoever does not find a pair of sandals, let him wear leather socks (*khuffayn*), and let him cut them below the ankles."