What is the ruling regarding continuing prayer if the ability to use water is found during a fast undertaken as substitution for Ghusl?
Chapter on Tayammum
Al-Mughni
Book of Purification
Primary text
Those who permit continuing the prayer argue by analogy that just as one who begins fasting as a substitute for having no neck (in expiation) is not required to exit the fast upon finding a slave to free, the current situation should allow continuation. Furthermore, they argue the person is not truly able to use the water because the ability requires invalidating the prayer, which is prohibited by the verse: {And do not invalidate your deeds} (Quran 33:33).
Supporting text
The opposing view cites the Hadith, 'The pure earth is the Muslim's purification even if he does not find water for ten years, but when you find water, let your skin touch it,' arguing its implication is that Tayammum is no longer purifying when water is found, and its explicit meaning demands touching the skin with water upon finding it. They also assert that since the person is capable of using water, the Tayammum is void, similar to one who leaves the state of prayer. Moreover, Tayammum is a purification of necessity, which ends when the necessity ceases, analogous to the purification of a woman with Istihada whose bleeding stops. Tayammum does not remove the underlying impurity; it only permits prayer due to the necessity of lacking water. Upon finding water, the necessity ends, and the state of impurity reappears. The analogy with fasting is rejected because fasting is the direct substitute itself; the difference is that the duration of fasting is long, making exiting difficult due to combining two arduous obligations, unlike this situation.