Is one who memorized the Qur’an then lost hold of it due to lack of revision and consolidation sinful?

Memorizing the Qur’an is a communal obligation (fard kifayah). Forgetting it, whether entirely or partially, after memorizing it, due to negligence and lack of revision, is a grave sin. Some scholars have even considered it among the major sins. The punishment for one who forgets it intensifies because of their negligence concerning a blessing from Allah Almighty, after their status had been elevated by its memorization. This abandonment leads to a return to ignorance. Some scholars are of the view that forgetting verses of the Qur’an after memorizing them constitutes ingratitude for the blessing.