وَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا قَامَ أَحَدُكُمْ مِنَ اللَّيْلِ ، فَاسْتَعْجَمَ الْقُرْآنُ عَلَى لِسَانِهِ فَلَمْ يَدْرِ مَا يَقُولُ ، فَلْيَضْطَجِعْ " .
And the Noble Prophet, peace and blessings be upon him, said: When any one of you wakes up at night and the Qur'an does not flow on his tongue, and he does not even know what he is saying (such is the effect of sleep), then he should lie down again.