Zirr bin Hubaish narrates: I presented myself before Safwan bin Assal Muradi. He inquired: Why have you come? I replied: To seek knowledge. He said: I heard the Prophet Muhammad (peace be upon him) say: "Whoever sets out from his house to seek knowledge, the angels, being pleased with his action, spread their wings for him." Zirr said: I have come to ask about wiping over leather socks (khuffs). He replied: Yes, we were in an army which the Prophet Muhammad (peace be upon him) had dispatched, and he instructed us that when we put on the leather socks in a state of purity (i.e., after performing ablution), we may wipe over them for three days during travel. After relieving ourselves (urinating or defecating), we would not remove them while performing ablution.