(23) باب اسْتِذْكَارِ الْقُرْآنِ وَتَعَاهُدِهِ
Narrated `Abdullah:
The Prophet (ﷺ) said, "It is a bad thing that some of you say, 'I have forgotten such-and-such verse of the Qur'an,' for indeed, he has been caused (by Allah) to forget it. So you must keep on reciting the Qur'an because it escapes from the hearts of men faster than camel do."
Reference: Sahih al-Bukhari 5032
In-book reference: Book 66, Hadith 54
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 6, Book 61, Hadith 550