Hishaam bin Kalbi Rahmatullah ‘Alayh once stated: “I had committed such a thing to memory which nobody had achieved before. I had memorized the entire Qur’an in a span of three days. In addition, I had forgotten something which nobody before had forgotten. When I had taken a scissors to trim my beard, I cut from above my fist instead of below it.”
[Shaami – Vol. 1, pg. 261]
Allah Ta’ala had allowed this to happen so that pride may not overcome him as a result of his extraordinary achievement.