Sunan Abi Dawud 21389
In-book no 885حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا خَالِدُ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سَعِيدٌ الْجُرَيْرِيُّ، عَنِ السَّعْدِيِّ، عَنْ أَبِيهِ، أَوْ عَنْ عَمِّهِ، قَالَ رَمَقْتُ النَّبِيَّ صلى الله عليه وسلم فِي صَلاَتِهِ فَكَانَ يَتَمَكَّنُ فِي رُكُوعِهِ وَسُجُودِهِ قَدْرَ مَا يَقُولُ " سُبْحَانَ اللَّهِ وَبِحَمْدِهِ " . ثَلاَثًا .
Sa’d reported that he heard his father or his uncle say ; I witnessed the Prophet (ﷺ) while offering prayer. He used to stay in his bowing and his prostration as long as one uttera the words “Glory be to Allah and praise be to Him” three times.