Musnad Ahmad 624:0

Safwan ibn 'Assal al-Muradi reported: I came to the Prophet (ﷺ) while he was in the mosque, reclining on a red garment of his. I said to him, "O Messenger of Allah, I have come seeking knowledge." He said, "Welcome, seeker of knowledge. Indeed, the angels surround the seeker of knowledge with their wings, then they gather one upon another until they reach the lowest heaven, out of love for what he is seeking." I said, "It has occurred to me to wipe over the leather socks after defecation, urination, or sleep, but I remember that you are the Messenger of Allah, so I wanted to ask you." He said, "Yes, for three days and their nights for the traveler, and for one day and one night for the resident."