From Sahih Muslim (Hadith 1841):
Abdullah reported Allah's Messenger (ﷺ) as saying:What a wretched person is he amongst them who says: I have forgotten such and such a verse. (He should instead of using this expression say): I have been made to forget it. Try to remember the Qur'an for it is more apt to escape from men's minds than a hobbled camel
Reference: Muslim 1841