Does the trickling of water droplets from a washed limb to another limb during ablution (wudu) or ritual bath (ghusl) affect the validity of the purification (tahara), given that this water becomes pure in itself, but not a purifier for other things?

The majority of scholars hold that water used in an obligatory purification is pure, but not purifying for anything else, and it is impermissible to use it for purification. This opinion is more cautious. If a small amount of used water mixes with pure water, it does not remove its purity. Therefore, if drops of ablution water fall on the hands, it does no harm. As for water falling from the upper part of the body to the lower part during ritual bathing (ghusl), it is not considered used; because the body of the one performing ghusl is like a single limb, and water is only deemed used after it separates from the limb.