I memorized the Muhkam during the time of the Messenger of Allah ﷺ. I asked him, "What is the Muhkam?"He replied, "The Mufassal."
جمعت المحكم في عهد رسول الله ﷺ فقلت له: وما المحكم؟ قال: المفصل.
Bukhari narrated it in the Virtues of the Quran (5036) from Yaqub bin Ibrahim, who said, Hushaym narrated to us, Abu Bishr informed us, from Saeed bin Jubayr, from Ibn Abbas, and he mentioned it.Ibn Abbas had memorized the mufassal surahs when he was ten years old, as Bukhari narrated in the Virtues of the Quran (5035) from Musa bin Ismail, who said, Abu Awana narrated to us, from Abu Bishr, from Saeed bin Jubayr, who said, What you call the mufassal is the muhkam. He said, Ibn Abbas said, "The Messenger of Allah ﷺ died when I was ten years old, and I had already read the muhkam."