 if you are impressed by your knowledge then know that you have no characteristic in it and that it is a gift from god alone that your lord has bestowed upon you so do not meet it with that which displeases him for perhaps he will make you forget it through an ailment with which he will test you which will cause you to forget what you have learned and memorized. i have been told about abdul malik bin tarif who was a man of knowledge intelligence moderate disposition and sound research that he had a great share of memory and hardly anything passed by his ears that needed to be recalled and that he boarded a ship and passed by it in a state of extreme terror that made him forget most of what he had memorized and greatly impaired the strength of his memory and that intelligence has not returned to him since. i was afflicted with an ailment and recovered from it and what i had memorized was gone except for what was immeasurable and i did not return to it except after years.
 وان أعجبت بعلمك فاعلم أنه لا خصلة لك فيه وأنه موهبة من الله مجردة وهبك اياها ربك تعالى فلا تقابلها بما يسخطه، فلعله ينسيك ذلك بعلة يمتحنك بها، تولد عليك نسيان ما علمت وحفظت. ولقد أخبرت عن عبد الملك بن طريف وهو من أهل العلم والذكاء واعتدال الأحوال وصحة البحث أنه كان ذا حظ من الحفظ عظيم، لا يكاد يمر على سمعه شيء يحتاج إلى استعادته، وأنه ركب البحر فمر به فيه هول شديد أنساه أكثر ما كان يحفظ وأخل بقوة حفظه اخلالا شديدا ولم يعاوده ذلك الذكاء بعد. وأنا أصابتني علة فأقمت منها، وقد ذهب ما كنت احفظ الا ما لا قدر له، فما عاودته الا بعد أعوام.