Sayyiduna Safwan bin Assal (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "When the traveller puts his feet (into the leather socks) in a state of purity, he may wipe over them for three days and nights, and he should not take them off because of defecation or urination, except for major ritual impurity (janabah)."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7333