Does the ablution of a woman experiencing Istihada (abnormal bleeding) become invalid immediately upon the cessation of the bleeding?
Chapter on Menstruation
Al-Mughni
Book of Purification
Primary text
If a woman experiencing Istihada performs ablution and her bleeding ceases, and it later becomes clear that the cessation was a temporary gap preceding her complete purity, then her previous ablution is invalidated by the cessation because the exiting impurity that was pardoned due to necessity is now subject to its inherent ruling once the necessity (bleeding) is removed. However, the apparent view attributed to Ahmad ibn Hanbal is that such temporary cessation is disregarded entirely.
Supporting text
Scholars such as Al-Qadi and Ibn Aqil hold that if the bleeding stops after ablution while she is still in the state of flowing blood, and she has no established habit of cessation, she must perform a new ablution before entering the prayer. This is because the temporary purity granted due to necessity ceases when the cause (bleeding) stops, thus revealing the ruling of the impurity, similar to a Tayammum performer finding water. If she enters the prayer during this cessation period, and the gap allows for ablution and prayer, her prayer is void because her previous purification is invalidated by the cessation.