Mishkat al-Masabih 8 The Excellent Qualities of the Qur’an كتاب فضائل القرآن 81

وَعَنْ قَتَادَةَ قَالَ: سُئِلَ أَنَسٌ: كَيْفَ كَانَتْ قِرَاءَةُ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ: كَانَت مدا مَدًّا ثُمَّ قَرَأَ: بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ يَمُدُّ بِبَسْمِ اللَّهِ وَيَمُدُّ بِالرَّحْمَنِ وَيَمُدُّ بِالرَّحِيمِ. رَوَاهُ البُخَارِيّ

Qatādā said that when Anas was asked how the Prophet recited the Qur’ān he replied that he did so prolonging the words. Then he recited “In the name of God, the Compassionate, the Merciful,” prolonging each phrase. Bukhārī transmitted it.