Sayyidina Abdullah (RA) reported that the Prophet (SAW) said, ‘How wrong it is for one of them or, for one of you to say, ‘I have forgotten such-and-such a verse’. Rather, he has been made to forget. Hence, keep revising the Quran, for, by Him in whose Hand is my soul, it is more liable to escape from hearts of people than an animal from its tether.”
[Ahmed 3620,Bukhari 5032,Muslim 790,Nisai 939]