Musannaf Ibn Abi Shayba 35:57

Al-Fadl ibn Dukayn narrated to us, from Zuhayr, from Abu al-Zubayr, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever does not find two sandals, let him wear two leather socks (khuffayn). And whoever does not find an izar (waist-wrapper), let him wear trousers (sarawil)."