Question
What is the ruling for a junub who began to pray with tayammum due to the cold, and then warm water was brought to him while he was in prayer?
Answer
I say, and with God's success: His ablution is invalidated, and he must perform ghusl and repeat the prayer; because the ability to use water nullifies the tayammum even if he is in prayer. Refer to: Al-Bahr Al-Ra'iq 1: 160, Radd Al-Muhtar 1: 170, and Sharh Al-Wiqayah p. 110, and God knows best.