question #3 Sahih Muslim 733a, Book 6, Hadith 142 : What can be learned from the Prophet’s (ﷺ) manner of reciting the Qur’an during prayers?

Never did I see the Messenger of Allah (ﷺ) observing supererogatory prayer sitting till one year before his death when he would observe Nafl prayer in a sitting position, and he would recite the Surah (of the Qur’an) in such a slow-measured tone (that duration of its recital) became more lengthy than the one longer than this.