Musnad Ahmad 624:5

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from 'Asim ibn Abi al-Najud, from Zirr ibn Hubaysh, who said: I came to Safwan ibn 'Assal al-Muradi, and he said: "What brought you?" I said: "I came seeking knowledge." He said: "For I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: 'There is no one who goes out from his house in pursuit of knowledge, except that the angels lower their wings for him, out of pleasure for what he is doing.'" He said: "I came to ask you about wiping over the leather socks (khuffayn)." He said: "Yes, I was in the army that the Messenger of Allah, peace and blessings of Allah be upon him, sent, and he commanded us to wipe over the leather socks if we put them on while in a state of purity, for three days when we are traveling, and for a day and a night when we are resident. And we should not take them off for defecation, nor for urination, nor for sleep, and we should not take them off except for major ritual impurity (janabah)." He said: "And I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: 'Indeed, in the West, there is a gate opened for repentance, the distance of which is seventy years; it will not be closed until the sun rises from its direction.'"