حَدَّثَنَا أَحْمَدُ بْنُ حَنْبَلٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ هَمَّامِ بْنِ مُنَبِّهٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِذَا قَامَ أَحَدُكُمْ مِنَ اللَّيْلِ فَاسْتَعْجَمَ الْقُرْآنُ عَلَى لِسَانِهِ فَلَمْ يَدْرِ مَا يَقُولُ فَلْيَضْطَجِعْ ‏"‏ ‏.‏

Narrated Abu Hurairah: The Messenger of Allah (PBUH) as saying: When one of you gets up by night (to pray), and falters in reciting the Qur'an (due to sleep), and he does not understand what he utters, he should sleep. Translation Not Available

Book Ref: Sunan Abi Dawud Book 5 Hadith 1311
Web Ref:  Sunan Abi Dawud Book 5 Hadith 1306