If a person praying experiences insinuating thoughts from Shaitan (Satan) in his salaat, causing him problems in reciting Quran, and resulting in bad or evil thoughts, and making him doubt the number of completed rakaat (iterations), what should he do?
This happened to one of the companions of the prophet (sahabah) whose name is Uthman Bin Abi Al-Aas, (may Allah be pleased with him), so he came complaining to the Prophet (peace be upon him), and he said: "The Shaitan comes between me and my salat and causes me problems with my recitation." So the Messenger of Allah, (peace be upon him), said: "That is a shaitan called Khanzab, so if you feel his presence, seek refuge in Allah and blow a mist to your left three times." He said: "I applied this advice and Allah has rid me off him."1 This hadith includes two ways to get rid off the shaitan of salat. The first is asking refuge in Allah from the shaitan's evil by pronouncing the words of seeking refuge and this is OK in this case. And the second: blowing with mist to the left three times. This is basically blowing air in a similar manner to spitting, but with a minute mist of saliva, on the condition that this does not disturb or bother the person next to him, nor make the masjid dirty.
From the book What Should You Do in the Following Situations... ?
1 Sahih Muslim 2203.