I have heard a hadith from the Messenger of Allah (peace and blessings be upon him) to the effect that: (Whoever memorizes a surah or a verse from the Noble Qur'an and then forgets it afterwards...

The questioner : I have heard a hadith from the Messenger of Allah (peace and blessings be upon him) to the effect that: What is the authenticity of this hadith, O honorable Shaykh?

The Shaykh : This hadith is narrated from the Prophet (peace and blessings be upon him) and contains a severe warning against whoever memorizes a verse from the Book of Allah and then forgets it. If this hadith is authentic, it refers to the one who forgets the verse out of negligence, turning away from the Book of Allah (Mighty and Majestic) and not caring about it.
As for the one who forgets it due to human nature or because he is preoccupied with what is obligatory upon him regarding the affairs of his life and the life of his family, he bears no sin. It is established from the Prophet (peace and blessings be upon him) that he forgot a verse in his prayer, and Abu ibn Ka'b (may Allah be pleased with him) reminded him of it after he had completed the prayer, so he said: meaning, before that. It is also established that he (peace and blessings be upon him) passed by a man reciting in his house and said: .
Forgetting is part of human nature, as the Prophet (peace and blessings be upon him) said: The strange thing is that some people, out of their fear of the punishment of Allah (Mighty and Majestic), are led by their desires to the point where they say: "I will not memorize anything from the Book of Allah, for I fear that I will memorize it and then forget it." Thus, they prevent themselves from good on the basis of this claim, which has no basis in truth. We say: Memorize the Book of Allah (Mighty and Majestic) and review it as much as you can, as the Prophet (peace and blessings be upon him) commanded, for he commanded the review of the Qur'an and said: So, you should memorize the Qur'an and review it. And if you forget something due to human nature, not out of turning away from the Book of Allah or negligence toward it, then that does not harm you, and you bear no sin.