Abū Mūsā al-Ash’arī reported God’s messenger as saying, “Keep refreshing your knowledge of the Qur’ān, for I swear by Him in whose hand my soul is that it is more liable to escape than camels which are tethered.” (Bukhārī and Muslim.)

عَنْ أَبِي مُوسَى الْأَشْعَرِيِّ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «تَعَاهَدُوا الْقُرْآنَ فَوَالَّذِي نَفْسِي بِيَدِهِ لَهْوَ أَشَدُّ تَفَصِّيًا مِنَ الْإِبِلِ فِي عُقُلِهَا»