Tayammum - AbsoluteAstronomy.com

Tayammum is the Islam

Islam

Islam . The most common are and . : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

ic act of dry ablution

Ritual purification

Ritual purification is a feature of many religions. The aim of these rituals is to remove specifically defined uncleanliness prior to a particular type of activity, and especially prior to the worship of a deity...

using sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

or dust

Dust

Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...

, which may be performed in place of ritual washing (wudu
Wudu
Wuḍhu is the Islamic procedure for washing parts of the body using water often in preparation for formal prayers...

or ghusl
Ghusl
Ghusl is an Arabic term referring to the full ablution required in Islam for various rituals and prayers. The ablution becomes mandatory for any adult Muslim after having sexual intercourse, any sexual discharge , completion of the menstrual cycle, giving birth, and death by natural causes.Islam...

) if no clean water is readily available.
Tayammum may be substituted for wudu or ghusl when access to water is restricted or impractical, namely:

When sufficient amounts of water for ritual washing are not available, including when using the available water for wudu or ghusl would leave insufficient water for drinking.
When obtaining water is hazardous or prohibitively expensive.
When using water poses a health risk.

Tayammum consists of the following steps:

Finding a piece of ground which is free of najaasah.