Reference : Hisn al-Muslim 138

أَعُوذُ بِاللَّهِ مِنَ الشَّيطَانِ الرَّجِيمِ، 
وَاتْفُلْ عَلَى يَسَارِكَ (ثلاثاً)
A`ūdhu billāhi minash-shayṭānir-rajīm.

(Say:) I seek refuge in Allah from Satan the outcast 
(then blow with a little spittle to your left). 
(Do this three times reciting in Arabic.)

Reference:
Muslim 4/1729.

Chapter: For one afflicted by whisperings in prayer or recitation