Question
What is the ruling for someone who began praying with tayammum due to illness, then was cured while in prayer?
Answer
I say, and with God's help: His tayammum is invalid, and he should perform ablution and repeat the prayer; because the ability to use water nullifies the tayammum even if he is in prayer. Refer to: Al-Hadiyah Al-Ala'iyah p. 38, and Sharh Al-Ziyadat vol. 3/part A, and God knows best.