Those Suras which you people call the Mufassal, are the Muhkam. And Ibn ʿAbbas said, "Allah's Apostle died when I was a boy of ten years, and I had learnt the Muhkam (of the Qur'an).  

إِنَّ الَّذِي تَدْعُونَهُ الْمُفَصَّلَ هُوَ الْمُحْكَمُ قَالَ وَقَالَ ابْنُ عَبَّاسٍ تُوُفِّيَ رَسُولُ اللَّهِ ﷺ وَأَنَا ابْنُ عَشْرِ سِنِينَ وَقَدْ قَرَأْتُ الْمُحْكَمَ  

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