Is it true that whoever memorizes the Quran and then forgets it incurs a penalty?

Learning, memorizing, and teaching the Quran are among the best acts of righteousness. Whoever memorizes it and is proficient in it will be with the noble and righteous scribes (angels). Forgetting the Quran is not a sin in itself, but it may be a punishment for some sins. Whoever memorized the Quran and then forgot it should strive to retrieve it, and there is no blame on him for that. The hadith (definition) that prohibits forgetting is weak. What Satan mentions, that forgetting the Quran after memorizing it is a sin, is from his whispers to divert the Muslim from memorizing the Quran. The Muslim should not surrender to these whispers and should strive in memorizing, reviewing, pondering, and acting upon it.