How is sleep categorized concerning its potential to invalidate ablution based on posture?
Chapter on What Nullifies Purification
Al-Mughni
Book of Purification
Primary text
Sleep is divided into three categories. First, sleep while lying down (*mudtaji'*) invalidates ablution, whether slight or extensive, according to all who hold sleep invalidates *wudu*. Second, sleep while sitting (*qa'id*): if extensive, it invalidates *wudu* based on one narration. This is the view of Hammad, al-Hakam, Malik, al-Thawri, and the people of *Ra'y*. Third, sleep while standing, bowing (*ruku'*), or prostrating (*sujud*). Regarding this third category, there are two narrations from Ahmad: one stating it invalidates *wudu* (the position of Shafi'i), as there is no specific text exempting these states from the general texts on invalidation, and they are not analogous to the sitting position where the place of impurity rests on the ground. The second narration is that it only invalidates if extensive.
Supporting text
Regarding sitting sleep, Shafi'i holds that even extensive sleep does not invalidate if the sitter is leaning and the place of impurity is resting on the ground, based on the narration that the companions of the Prophet (peace be upon him) would sleep while waiting for *Isha* and then pray without renewing *wudu*. This suggests that if one is careful against the exit of impurity, *wudu* is not invalidated, similar to slight sleep. Abu Hanifa maintained that sleep during any posture of prayer does not invalidate *wudu*, even if extensive, citing a narration that the Prophet (peace be upon him) slept in prostration and then prayed without ablution, stating *wudu* is only required for one who sleeps lying down because their joints relax then.