Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this same chain of narration, it is reported from (Sayyiduna Ibn Umar, may Allah be pleased with them both) that the Messenger of Allah, peace and blessings be upon him, forbade the person in ihram from wearing such cloth that has been dyed with saffron or (fragrant herb) wars. And the Prophet, peace and blessings be upon him, said: "Whoever does not have open sandals (slippers), then he should wear socks (and boots) and cut them below the ankles."