Shaqiq reported,

Abdullah said, "Take care of these copies of the Quran," and sometimes he said, "the Quran, for it slips away from the hearts of men more swiftly than livestock break free from their tethers."He said, and the Messenger of Allah ﷺ said, "None of you should say, 'I forgot such-and-such a verse.' Rather, he was made to forget."

Muslim 1842

Sahih

حدثنا ابن نمير حدثنا أبي وأبو معاوية ح و حدثنا يحيى بن يحيى واللفظ له قال أخبرنا أبو معاوية عن الأعمش

عن شقيق قال

قال عبد الله تعاهدوا هذه المصاحف وربما قال القرآن فلهو أشد تفصيا من صدور الرجال من النعم من عقله قال وقال رسول الله ﷺ لا يقل أحدكم نسيت آية كيت وكيت بل هو نسي

مسلم 1842صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Virtues of the Quran and what relates to it
Chapter
Command to constantly review the Quran and the dislike of saying "I forgot such and such a verse", and the permissibility of saying "I was made to forget it"
Numbering
Darussalam 1842
Muslim 1842