Ibn Abbas (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) addressed us at Arafat and said: "Whoever cannot find a waist-wrapper (izar) may wear trousers, and whoever cannot find sandals may wear leather socks (khuffs)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9065
Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said that he heard the Messenger of Allah (peace and blessings be upon him) delivering a sermon, saying: "When the person in ihram (muhrim) does not find sandals, let him wear leather socks (khuffs), and when he does not find a waist-wrap (izar), let him wear trousers."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9066
Likewise (through another chain), with this addition: Amr said: Ibn Abbas did not mention cutting, while Ibn Umar said: "And let him cut them until they are below the ankles." So I do not know which of the two hadiths abrogated the other.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9067
Ibn Umar (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "When the person in ihram does not find sandals, let him wear leather socks, and let him cut them until they are below the ankles."
Imam al-Shafi'i (may Allah have mercy on him) said: The leather socks should indeed be cut below the ankles, because this is found in the hadith of Ibn Umar (may Allah be pleased with them both), even though it is not found in the hadith of Ibn Abbas (may Allah be pleased with them both), and they are both truthful and precise.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9068
Sayyiduna Jabir (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever does not find sandals, let him wear leather socks, and whoever does not find a waist-wrap, let him wear trousers."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9069