Question 10: A person performed Wudoo’ (ablution), and because of a wound in his hand that should not be exposed to water, he performed Tayammum (dry ablution with clean earth) for that area. It happened that he once forgot to do Tayamum for the wounded area, but during Salaah (Prayer) he remembered, so he performed Tayammum without interrupting the Salaah and continued praying. What is the ruling on this Salaah? Is it valid or not?
Answer: All praise be to Allaah Alone, and peace and blessings be upon the Messenger of Allaah, his family and Companions. To proceed: If one of the body parts required to be washed in Wudoo’ sustains a wound that must not be washed or wiped with water, as this may worsen the wound or slow the healing, the person should perform Tayammum... read more here.