Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) was asked about the ruling on wiping the face with the hands after making du’aa’. He replied: 

Wiping the face with the hands after making du’aa’ is more likely to be not prescribed in Islam, because the ahaadeeth that have been narrated concerning that are da’eef (weak). Shaykh al-Islam (may Allaah have mercy on him) said: They cannot be used as evidence. If we are not certain or we think it most likely that this is not prescribed, then it is better not to do it, because Islamic rulings cannot be proven on the basis of mere conjecture, unless we believe it to be mostly likely to be the case. 

What I think about wiping the face with the hands after du’aa’ is that it is not Sunnah. As is well known, the Prophet (peace and blessings of Allaah be upon him) prayed for rain during his Friday khutbah and raised his hands, but it is not narrated that he wiped his face with them. Similarly in a number of ahaadeeth it says that the Prophet raised his hands, but there is no proof that he wiped his face. End quote. 

Majmoo’ Fataawa Ibn ‘Uthaymeen, 14/question no. 781