Ibn Hibban

Sayyiduna Abu Hurairah, may Allah be pleased with him, narrates this statement of the Prophet Muhammad, peace and blessings be upon him: "When the call to prayer (adhan) is given, Satan turns his back and runs away, passing wind as he goes (he goes so far) until he does not hear the sound of the adhan. When the adhan is completed, he comes back. Then when the call for the commencement of prayer (iqamah) is given, he again turns his back and goes away. When the iqamah is completed, he comes back again. He starts putting thoughts into a person's mind and says, 'Remember such-and-such thing, remember that thing,' things which he would not have remembered otherwise. Until, when a person is performing prayer, sometimes it happens that he does not know how much he has prayed."