How is doubt concerning the state of ritual purity (Wudu) adjudicated?
Chapter on What Nullifies Purification
Al-Mughni
Book of Purification
Primary text
If one is certain of having performed ablution but doubts whether they have subsequently nullified it, they should proceed based on their certainty of purity (i.e., they remain in a state of Wudu). Conversely, if one is certain of having nullified ablution but doubts whether they have subsequently performed Wudu, they remain in a state of impurity. In both cases, one must abide by what was known before the doubt arose and discard the doubt. This is the position of ath-Thawri, the people of Iraq, al-Awza'i, ash-Shafi'i, and all scholars known to us.
Supporting text
Al-Hasan and Malik hold different views. Al-Hasan stated that if one doubts the occurrence of an impurity during prayer, they should complete the prayer, but if the doubt arises before entering the prayer, they must perform ablution. Malik ruled that if one frequently experiences doubt regarding impurity, they should remain on their current state of ablution; however, if such doubt is infrequent, they must perform ablution, as one should not enter prayer while doubting.