Sahih al-Bukhari 3285

Narrated Abu Huraira:

The Prophet (ﷺ) said, “When the call for the prayer is pronounced, Satan takes to his heels, passing wind
with noise, When the call for the prayer is finished, he comes back. And when the Iqama is
pronounced, he again takes to his heels, and after its completion, he returns again to interfere between
the (praying) person and his heart, saying to him. ‘Remember this or that thing.’ till the person forgets
whether he has offered three or four rak`at: so if one forgets whether he has prayed three or four rak`at,
he should perform two prostrations of Sahu (i.e. forgetfulness).