What is meant by "Nadh" (sprinkling/dabbing), and does it purify ritual impurity?

Nadh is sprinkling water without it flowing. Nadh is not sufficient to wash away impurity if the garment is certainly soiled by it; rather, it must be washed. The proof for this is the hadith of Umm Qais bint Mihsan, who came with a young son of hers who had not yet eaten food, and he urinated on the Prophet's garment (peace be upon him). So, he sprinkled water on it and did not wash it, which indicates that nadh is not sufficient if the child has eaten food. However, if you are unsure whether the garment has been soiled by urine, sprinkling is sufficient.