Question: It is commanded in Islam that when water is not available you must instead of Wudhu (ablution) and Ghusl (bath) perform the Tayammum on soil/earth etc. But how can Tayammum be performed on soil, when all sorts of germs are present in it? And they can be transferred through the soil?
Answer: As proved by medical sciences clean and unpolluted soil is safe from germs and most germs cannot survive in soil. The reason soil is so protective is very tiny living things that exist in soil are deadly enemies of harmful germs.
For example a dead body in which millions and billions of germs are present is buried in the earth, then these small living beings immediately starts assimilating that corpse and very soon they defeat the army of germs and destroy them.
Therefore contrary to what people think clean pure and unpolluted soil does not have germs and it is a vital enemy of germs and sooner or later it destroys them.
Keeping this in view it seems that when water is not available in command of Islam to do Tayammum on soil is according to the discovery of Medical science.
The basic point to note with regard to this is that in Qur’an the verse of Tayammum emphasizes that the soil be clean and pure. It says:
And (if) you cannot find water, betake yourselves to pure earth, then wipe your faces and your hands…1
With regard to this religious command, the traditions of Holy Imams (a.s.) state that soil should be pure, clean and clear. In the book Wasaelush Shia Imam as-Sadiq (a.s.) has been quoted thus:
“Do not take the soil for Tayammum from such places, which are thoroughfares, and people are passing through it.”
This emphasis is there because generally the chance of such places being polluted is more, but those places where people do not passing through generally remains clean and pure.