Sayyiduna Abdullah bin Umar (may Allah be pleased with him) says that a man asked the Messenger of Allah (peace and blessings be upon him): Which clothes should the one in ihram wear? He (peace and blessings be upon him) said: "Do not wear shirts, turbans, trousers, hooded cloaks (burnus), garments touched by saffron or wars, or leather socks (khuffs). But if someone cannot find sandals, he may wear leather socks, cutting them below the ankles."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9058