If a person who has performed tayammum finds water and hopes to find more water later or thinks he might find it as intended but then struggles to find it, merely seeing the water invalidates his tayammum, and he must repeat it. If he finds water after starting his prayer but has not yet bowed (Rukuh), he should interrupt and perform wudu. If he has already bowed, he should continue with his prayer, as tayammum is one of the forms of purification. If a person performs tayammum and later finds water, he must perform ghusl if he was in a state of janabah or wudu if he was not, but if he has already completed his prayer with tayammum during its time, then his prayer is valid and does not need to be repeated.
