What is the ruling concerning sleep invalidating ablution?
Chapter on What Nullifies Purification
Al-Mughni
Book of Purification
Primary text
Sleep invalidates ablution according to the general opinion of scholars. Evidence for this includes the narration of Safwan ibn Assal, which lists sleep alongside feces and urine as causes for removing ritual purity. Furthermore, the Prophet (peace be upon him) stated, "The eye is the tether of the anus, so whoever sleeps must perform ablution." Sleep is considered a proxy for impurity because it is a probable cause for impurity, analogous to the joining of circumcised parts necessitating *ghusl* in place of actual ejaculation.
Supporting text
A minority view, attributed to Abu Musa al-Ash'ari, Abu Mijlaz, and Humayd al-A'raj, holds that sleep does not invalidate *wudu*. Some, like Sa'id ibn al-Musayyib, slept while waiting for prayer and then prayed without renewing ablution. Their reasoning may be that sleep itself is not an impurity (*hadath*), and since impurity is doubtful, certainty of purity should not be removed by doubt.