It was narrated from Khuzaimah bin Thabit that:
The Prophet said: "Three days." I think he said, "And three nights during which the traveler may wipe over his leather socks." (JA)
English reference (JA): Vol. 1, Book 1, Hadith 554 (JA)
Arabic reference (JA): Book 1, Hadith 597 (JA)