It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger (peace and blessings of Allah be upon him) said: "If a pilgrim in the state of Ihram does not find shoes, he should wear socks, but he should cut them below the ankles."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4454