Yahya related to me from Malik from Abu'z-Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "When the call to prayer is made Shaytan retreats, passing wind, so that he will not hear the adhan. When the adhan is completed he comes back, until, when the iqama is said, he retreats again. When the iqama is completed, he comes back, until he comes between a man and his self and says, 'Think of such and such, think of such and such,' which he was not thinking about before, until the man does not know how much he has prayed."

Muwatta Malik Book 3, Hadith 6