Zirr bin Hubaysh al-Asadi (may Allah have mercy on him) says that he came to Sayyiduna Safwan bin Assal al-Muradi (may Allah be pleased with him), who was one of the Companions who used to be asked (about rulings). He asked: "What do you need?" We said: "We have set out today in search of knowledge." He said: "Whoever leaves his house in search of knowledge, the angels spread their wings for both the learner and the scholar." I asked him about wiping over the leather socks, and he said: "Yes, the Messenger of Allah (peace and blessings be upon him) was asked, and he (peace and blessings be upon him) set three days and nights for the traveller and a day and a night for the resident, except for major ritual impurity (janabah); but for defecation, urination and sleep (there is no need to take them off)."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7319