ENOfficial
Narrated Sa`id bin Jubair: Those Suras which you people call the Mufassal, are the Muhkam. And Ibn `Abbas said, "Allah's Apostle died when I was a boy of ten years, and I had learnt the Muhkam (of the Qur'an).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، قَالَ إِنَّ الَّذِي تَدْعُونَهُ الْمُفَصَّلَ هُوَ الْمُحْكَمُ، قَالَ وَقَالَ ابْنُ عَبَّاسٍ تُوُفِّيَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَنَا ابْنُ عَشْرِ سِنِينَ وَقَدْ قَرَأْتُ الْمُحْكَمَ.
sunnah.com