Messenger of Allah ﷺ said, "The example of the person who knows the Qur'an by heart is like the owner of tied camels. If he keeps them tied, he will control them, but if he releases them, they will run away."  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِنَّمَا مَثَلُ صَاحِبِ الْقُرْآنِ كَمَثَلِ صَاحِبِ الإِبِلِ الْمُعَقَّلَةِ إِنْ عَاهَدَ عَلَيْهَا أَمْسَكَهَا وَإِنْ أَطْلَقَهَا ذَهَبَتْ  

The Prophet ﷺ said, "It is a bad thing that some of you say, 'I have forgotten such-and-such verse of the Qur'an,' for indeed, he has been caused (by Allah) to forget it. So you must keep on reciting the Qur'an because it escapes from the hearts of men faster than camel do."  

قَالَ النَّبِيُّ ﷺ بِئْسَ مَا لأَحَدِهِمْ أَنْ يَقُولَ نَسِيتُ آيَةَ كَيْتَ وَكَيْتَ بَلْ نُسِّيَ وَاسْتَذْكِرُوا الْقُرْآنَ فَإِنَّهُ أَشَدُّ تَفَصِّيًا مِنْ صُدُورِ الرِّجَالِ مِنَ النَّعَمِ  

I heard the Prophet ﷺ saying... (as above, no. 550).  

سَمِعْتُ النَّبِيَّ ﷺ  

The Prophet ﷺ said, "Commit yourself to the Qur'an, for by Him in whose Hand is my soul, it is surely more prone to break away than a camel in its bind.  

عَنِ النَّبِيِّ ﷺ قَالَ تَعَاهَدُوا الْقُرْآنَ فَوَالَّذِي نَفْسِي بِيَدِهِ لَهُوَ أَشَدُّ تَفَصِّيًا مِنَ الإِبِلِ فِي عُقُلِهَا