The extent of sickness that permits a person to perform Tayammum

Q: What is the extent of sickness that permits a person to perform Tayammum (dry ablution with clean earth), even if water is available?

A: All praise be to Allah Alone, and peace and blessings be upon His Messenger, and his family and Companions. The extent of any sickness in which it is permissible for a person to perform Tayammum, is if using water may aggravate the sickness or delay the process of the healing of wounds.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.