[Machine] Indeed, the one you call the "elaborate" is the "firmly established." The Messenger of Allah ﷺ passed away and I was ten years old when I read the "firmly established."
إِنَّ الَّذِي تَدْعُونَهُ الْمُفَصَّلَ هُوَ الْمُحْكَمُ تُوُفِّيَ رَسُولُ اللهِ ﷺ وَأَنَا ابْنُ عَشْرِ سِنِينَ وَقَدْ قَرَأْتُ الْمُحْكَمَ
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