The Messenger of Allah ﷺ taught me to recite, "And We have certainly made the Quran easy for remembrance, so is there any who will remember?" [Qamar 54:17] with the word "muddakir."A man asked, "Abu Abdul-Rahman, is it 'muddakir' or 'mudhakir'?"He replied, "The Messenger of Allah ﷺ taught me to recite it as 'muddakir.'"
حدثنا حجاج حدثنا إسرائيل عن أبي إسحاق عن الأسود
أقرأني رسول الله ﷺ {ولقد يسرنا القرآن للذكر فهل من مدكر} فقال رجل يا أبا عبد الرحمن مدكر أو مذكر قال أقرأني رسول الله ﷺ مدكر
No references are available.
Its isnad is sahih. Bukhari narrated it, 8:475, through several routes from Abu Ishaq in abridged form, and Abu Dawud likewise narrated it, 4:62, in abridged form. In Dhakhair, 4870, it is stated that Muslim and Tirmidhi also narrated it.