Purity: Wiping When Moisture on Hands Dries
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 256
If for the purposes of wiping, no moisture is left on the hand such that both arms are dry from the elbow to the tips of the fingers, one cannot wet his hands with additional water; rather, one must take moisture from his beard and perform the wiping with that. Taking moisture from anything other than one’s beard and wiping with it is problematic [i.e. based on obligatory precaution, such a wiping does not suffice].
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)