سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 1072
The Book of The At-Tatbiq (Clasping One's Hands Together)
The Qunut during the Subh prayer
أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا بِشْرُ بْنُ الْمُفَضَّلِ، عَنْ يُونُسَ، عَنِ ابْنِ سِيرِينَ، قَالَ حَدَّثَنِي بَعْضُ، مَنْ صَلَّى مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم صَلاَةَ الصُّبْحِ فَلَمَّا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ . فِي الرَّكْعَةِ الثَّانِيَةِ قَامَ هُنَيْهَةً .
It was narrated that Ibn Sirin said: "Some of those who prayed the Subh prayer with the Messenger of Allah (ﷺ) narrated to me that when he said: Sami'Allahu liman hamidah (Allah hears those who praise Him)' in the second rak'ah, he stood for a while."
Sunan an-Nasa'i, 1072Sahih (Darussalam)