It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he heard the Messenger of Allah (peace and blessings be upon him) say: 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 / 5906
Hadith Gradingحکم دارالسلام:حديث صحيح، مؤمل - وإن كان سيئ الحفظ - تابعه أبو أحمد الزبيري.