Jami` at-Tirmidhi 2942
جامع الترمذي#2942SahihNarrated 'Abdullah:that the Prophet (ﷺ) said: "How horrible it is for one of them - or - one of you to say: "I have forgotten such and such Ayah,' rather he was made to forget. So be mindful of the Qur'an, for - by the One in Whose Hand is my soul - it escapes from men's hearts faster than a camel from its fetter
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 46:16