What is the ruling on forgetting the Qur'an after memorizing it?

Question : The questioner asks: What is your opinion regarding the hadith and then he forgot it?

Answer : There is also a concern regarding the authenticity of this hadith. Forgetting a verse of the Qur'an has happened even to the Messenger (peace and blessings be upon him). The Prophet (peace and blessings be upon him) led his Companions in prayer one day, and when he finished the prayer, Ubayy ibn Ka'b reminded him of a verse he had forgotten. The Prophet said, "Why did you not remind me of it?" On one occasion, he passed by a man reciting the Qur'an, praised him, and said, "I think Allah has mercy on so-and-so; he reminded me of a verse I had forgotten." Forgetting a verse of the Qur'an is something that befalls all of humanity, and such a warning cannot apply to something that befalls all of humanity. However, if a person memorizes something of the Qur'an and does not raise his head with it—meaning he does not act upon it—and is negligent regarding it, then he may be subject to some punishment, though we do not assert this with certainty. As for if his forgetting occurs despite his earnestness regarding the Qur'an and its study, but he forgets it due to his human nature...