Praise be to Allah.
There is no basis for that as far as we know. Rather it is disliked to do that before saying the salaam, because it is proven that the Prophet (blessings and peace of Allah be upon him) said the salaam at the end of Fajr prayer on a rainy night, and traces of water and mud could be seen on his face. This indicates that the best is not to wipe it off before finishing the prayer. End quote.
Shaykh Ibn Baz (may Allah have mercy on him).
Tuhfat al-Ikhwan (p. 61).
And Allah knows best.