Does the complete drying of an impurity, so that no trace of its color, taste, or smell remains, purify the contaminated spot—such as urine and semen mixed with pre-ejaculatory fluid on a rug—or is it obligatory to pour water on the spot of the impurity?

Most scholars believe that if urine or prostatic fluid (madhy) stains a bed or similar item, and its physical trace (color, taste, smell) completely disappears, it does not become pure by drying alone; rather, it must be purified with water.

There is another opinion, chosen by Sheikh al-Islam Ibn Taymiyyah, that impurity becomes pure if its physical trace completely disappears by any means of removal, including the sun and wind. This is because removing impurity is not an act of worship in itself, but rather the elimination of a foul substance.

Accordingly, the opinion that impurity becomes pure by the disappearance of its trace through the sun or wind is a valid one. However, the view of the majority (requiring water) is more cautious.