Tayammum
Tayammum is using sand with the purpose of purification instead of doing wudu or major ablution.
Tayammum is allowed when:
1. there is no water.
2. One is not able to use water due to sickness, or the need for water or it is too cold that it can cause harm.
Tayammum description:
1. State al-niyyah in the heart.
2. Hit the ground or anything that is attached to it like walls.
3. Rub the face and back of the hands..
He who is not able to do wudu or tayammum and does not find anyone to purify him and is afraid that the time of prayer will end: can pray with that status for necessity