Ibn ʿAbbas said, "I have learnt all the Muhkam Suras during the life time of Messenger of Allah ﷺ." I said to him, 'What is meant by the Muhkam?" He replied, "The Mufassal."
عَنِ ابْنِ عَبَّاسٍ ؓ جَمَعْتُ الْمُحْكَمَ فِي عَهْدِ رَسُولِ اللَّهِ ﷺ فَقُلْتُ لَهُ وَمَا الْمُحْكَمُ قَالَ الْمُفَصَّلُ
[Machine] I collected Al-Muhkam during the time of the Messenger of Allah ﷺ, and the Prophet ﷺ passed away while I was only ten years old and having memorized ten chapters. I asked him, "What is Al-Muhkam?" He said, "It is the well-explained."
جَمَعْتُ الْمُحْكَمَ فِي عَهْدِ رَسُولِ اللهِ ﷺ وَقُبِضَ النَّبِيُّ ﷺ وَأَنَا ابْنُ عَشْرِ حِجَجٍ قَالَ فَقُلْتُ لَهُ وَمَا الْمُحْكَمُ؟ قَالَ الْمُفَصَّلُ