Sahih Muslim Book 4, Hadith Number 1721.

Chapter : Concerning dozing off in prayer, or faltering of one’s tongue in the recitation of the Qur’an, or in mentioning of Allah, one should sleep, or stop it till one becomes lively.

‘Aisha reported that the Apostle of Allah (may peace be upon him) listened to the recitation of the Qur’an by a man in the mosque. Thereupon he said: May Allah have mercy upon him; be reminded me of the verse which I had been made to forget.