Think a stain is gone because it dried? Not so fast — here’s the quick rule about when a physical impurity is really considered removed in Islamic law
In Islam, the removal of the physical impurity (zawāl ʿayn najāsat) means the complete elimination of the actual bodily impurity from its place. In other words, the ʿayn (the substance or bulk of the impurity) must be entirely removed so that no trace of it remains.
By “removal of the physical impurity” we mean that even the tiny particles of the impurity are eliminated; if, for example, urine dries up, the physical impurity is considered removed.
For example, if blood spills on a garment, as long as the bloodstain and its substance remain on the cloth, the garment is impure. But if the blood is completely washed away and no trace remains, the physical impurity has been removed and the garment becomes pure.
Removal of the physical impurity is a required condition for the purification of an impure item or place. That is, until the physical impurity is removed, the impure place is not purified.
However, in some cases — such as internal impurities of the body (for example inside the mouth or nose) — purification is achieved simply by the removal of the physical impurity, and water-based purification is not required.
Regarding the disappearance of the trace of impurity, some jurists hold that in addition to the removal of the physical impurity, the removal of its traces — i.e., the fine particles that are usually removed by water — is also a condition for purification. But other jurists consider the removal of the physical impurity alone to be sufficient for purification.
