Sahih Muslim Book 26, Hadith Number 5463.

Chapter : Seeking refuge against satan from the evil promptings in prayer.

Uthman b. Abu al-‘As reported that he came to Allah’s Messenger (may peace be upon him) and said: Allah’s Messenger, the Satan intervenes between me and my prayer and my reciting of the Qur’an and he confounds me. Thereupon Allah’s Messenger (may peace be upon him) said:, That is (the doing of the Satan) who is known as Khinzab, and when you perceive its effect, seek refuge with Allah from it and spit three times to your left. I did that and Allah dispelled that from me.