Zirr bin Hubaysh (may Allah have mercy on him) narrates: I came to Sayyiduna Safwan bin Assal (may Allah be pleased with him) to ask him about wiping over the leather socks, and he said: "The Messenger of Allah (peace and blessings be upon him) used to order us on journeys not to take off our leather socks for three days and nights, except for major ritual impurity (janabah); but for sleep, defecation and urination (wiping is sufficient)."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7320