Prolonging certain sounds while reciting the Qur'an Sahih al-Bukhari 5046

Arabic hadith text
حَدَّثَنَا عَمْرُو بْنُ عَاصِمٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، قَالَ سُئِلَ أَنَسٌ كَيْفَ كَانَتْ قِرَاءَةُ النَّبِيِّ صلى الله عليه وسلم‏.‏ فَقَالَ كَانَتْمَدًّا‏.‏ ثُمَّ قَرَأَ بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ، يَمُدُّ بِبِسْمِ اللَّهِ، وَيَمُدُّ بِالرَّحْمَنِ، وَيَمُدُّ بِالرَّحِيمِ‏.‏
Translation
Narrated Qatada

Anas was asked, "How was the recitation (of the Qur'an) of the Prophet?' He replied, "It was characterized by the prolongation of certain sounds." He then recited: In the Name of Allah, the Most Beneficent, the Most Merciful prolonging the pronunciation of 'In the Name of Allah, 'the most Beneficent,' and 'the Most Merciful.