The reward from Allah (swt) for committing the Glorious Qur’an to memory is very great. The ahadith elaborating this are many, as well as those explaining the high status of the one who has memorised the Qur’an. Nowadays we call such a person a ‘Hafiz al-Qur’an – the protector of the Qur’an’ but in the past he would be known as ‘Haamil al-Qur’an – the bearer of the Qur’an’. And despite this being a great blessing and favour on such a person, it is at the same time a heavy load to carry. Allah (swt) says:
إِنَّا سَنُلْقِي عَلَيْكَ قَوْلا ثَقِيلا
We will cast upon you a weighty Word. (al-Muzzammil: 5)
لَوْ أَنْزَلْنَا هَذَا الْقُرْآنَ عَلَى جَبَلٍ لَرَأَيْتَهُ خَاشِعًا مُتَصَدِّعًا مِنْ خَشْيَةِ اللَّهِ
If We had sent down this Qur’an onto a mountain, you would have seen it humbled, crushed to pieces out of fear of Allah. (al-Hashr: 21)
Part of the burden of carrying this Qur’an is that it constantly needs to be revised. And one cannot be negligent about this. Rasulullah (saw) has mentioned this in a hadith where he says:”Persist and devote yourselves to the recitation of this Qur’an, for by Him in Whose Hand lies the soul of Muhammad, it slips way faster than camels that are released from their tethers.” (Sahih Bukhari) And also: “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.” (Sahih Bukhari)
Although those who memorise the Qur’an have been praised highly by Allah and His Rasul, a severe warning has also been issued to them should they forget that which they previously learnt. The Prophet (saw) said: “The good deeds of my Ummah were displayed to me, even (the smallest of deeds such as) a speck (of dust) which a man removes from the mosque; and the sins of my Ummah were displayed to me and I did not see any sin greater than a man who was given a chapter or a verse from the Qur’an, and then he forgot it.” (Tirmidhi) And also:”Whoever recites the Qur’an and thereafter forgets it will meet Allah on the Day of Judgment as a leper.” (Abu Dawud)
Allahumma dhakkirnaa minhu maa naseenaa, wa ‘allimnaa minhu maa jahilnaa.
O Allah, make us remember that which we have forgotten of it, and teach us that which we are ignorant of it.
See also: An Encouragement for the Huffaz.
 These last two ahadith are weak.