مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٣٩ - PURIFYING THINGS

does not serve as an impediment between the impure thing and the sun.
(iv) Only the sun should make the impure thing dry. Hence, if an impure thing becomes dry, for example, with wind as well as with the sun, it will not become pure. However, it does not matter if the wind u so light that it may not be said that it has had any share in making the impure thing dry.
(v) The sun should dry up, in one instance, the whole impure part of the building, and in case the sun dries in the first instance, the surfaceof the impure earth or building, and in the second instance the inner part becomes dry, only the outer part will become pure and the inner portion will remain impure.
١٩٣. It is difficult to say that an impure mat may be made pure by the sun, but the sun purifies trees and the grass which have not been cut yet.
١٩٤. If the sun shines on impure earth and a doubt arises later whether the earth was wet or not at the time of sunshine and whether the wetness dried up with sunshine or not the earth will remain impure. And the position will also be the same (i.e. the earth will remain impure) if doubt arises as to whether the original impurity was removed from the earth or not, or whether anything prevented the sun from shining on the earth or not.
١٩٥. If the sun shines on one side of an impure wall and as a consequence of it the other side of the wall also becomes dry it is not improbable that both the sides may be purified.

IV. TRANSFORMATION (ISTIHALA)
١٩٦. If an impure thing undergoes such a change that it assumes the shape of a pure thing it becomes pure; for example, if an impure piece of wood burns and is reduced to ashes or a dog falls in a salt-marsh and becomes salt it becomes pure. But the thing does not become pure if its essence does not change; for example, if wheat is ground into flour or is used for baking bread it does not become pure.