(33) باب الأَمْرِ بِتَعَهُّدِ الْقُرْآنِ وَكَرَاهَةِ قَوْلِ نَسِيتُ آيَةَ كَذَا. وَجَوَازِ قَوْلِ أُنْسِيتُهَا
'Abdullah b. 'Umar reported Allah's Messenger (ﷺ) as saying:
The example of a man who has memorised the Qur'an is like that of a hobbled camel. If he remained vigilant, he would be able to retain it (with him), and if he loosened the hobbled camel it would escape.
Reference: Sahih Muslim 789 a
In-book reference: Book 6, Hadith 267
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1722