Musnad Abu Ya'la al-Mawsili 3:300

Ubayd Allah ibn Umar narrated to us, Yunus ibn Arqam narrated to us, Yazid ibn Abi Ziyad narrated to me, from al-Qasim ibn Mukhaymirah, from Shurayh ibn Hani, who said: I came to Ali and asked him about wiping over the leather socks (khuffayn). He said: "We were with the Messenger of Allah, may Allah bless him and grant him peace, on a journey, and we wiped for three days and their nights, and for the resident, one day."