It is narrated from Sayyiduna Khuzaymah bin Thabit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) ordered us: "When we are resident, we should wipe over our leather socks for a day and a night, and when we are travelling, for three days and three nights." And by Allah, had the questioner kept on asking, he (peace and blessings be upon him) would have made it five days. (b) In the narration of Imam al-Thawri (may Allah have mercy on him) it says: Had I asked him for more time, he (peace and blessings be upon him) would have given us more.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1320