Sahih al-Bukhari 3285

Muhammad ibn Yusuf narrated to us: al-Awzaʿi narrated to us, from Yahya ibn Abi Kathir, from Abu Salama, from Abu Hurayra (may Allah be pleased with him), who said: The Prophet ﷺ said: ‘When the call to prayer is made, Satan turns away, passing wind noisily. When it is finished, he returns. When the call announcing that the prayer is about to begin is made, he turns away again; when it is finished, he returns and intrudes between a person and his heart, saying, “Remember this and that,” until the person no longer knows whether he prayed three or four units. If he does not know whether he prayed three or four, he performs two prostrations for forgetfulness.’