Perform tayamumm when water isn't available or if someone cannot use it due to illness or injury; find some good earth; wipe your face & arms up until the elbows; pray as usual afterwards .

This hadith is about a practice called tayammum which is a substitute for wudu. It is done when water is not available or if someone cannot use water due to illness or injury. To perform tayammum one must find some good earth and wipe their face and arms up to the elbows with it. After that they can pray as usual. This hadith teaches us that even in difficult situations we should still strive to fulfill our religious obligations such as prayer.