Sunan Ibn Majah Book 1, Hadith 212

"The Messenger of Allah used to command us not to take off our leather socks for three days except in the case of sexual impurity, but not in the case of defecation, urine or sleep (i.e. during travel)."

Previous Hadith

The Messenger of Allah said: "The eye is the leather strap (that ties up) the anus, so whoever falls asleep, let him perform ablution."

Sunan Ibn Majah Book 1, Hadith 211
Next Hadith

"The Messenger of Allah said: 'If anyone of you touches his penis, let him perform ablution.'"

Sunan Ibn Majah Book 1, Hadith 213