Sayyiduna Safwan bin Assal (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) used to instruct us that when we were on a journey, we should not take off our leather socks for three days and nights except for major ritual impurity (janabah); but for urination, sleep and defecation (we should not take them off).
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7326