Is it an act of Sunnah (supererogatory act of worship following the example of the Prophet) to wipe one's face with the hands after finishing Salah (prayer)?
This is not an act of Sunnah and we do not know that the Prophet (peace be upon him) ever reported this either verbally, or by practice, neither have the Sahabah (Companions of the Prophet, may Allah be pleased with them). Thus, following the Prophet (peace be upon him) is absolute goodness and all the evil lies in introducing Bid`ahs (innovations in religion). (Part No. 7; Page No. 73) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.