The Book of The At-Tatbiq (Clasping One's Hands Together)
12/21. Chapter:
What the Imam says when he raises his head from bowing
Sunan an-Nasai
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، قَالَ حَدَّثَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ قَالَ " اللَّهُمَّ رَبَّنَا وَلَكَ الْحَمْدُ " .
It was narrated that Abu Hurairah said: "When the Prophet (ﷺ) raised his head from bowing, he said: 'Allahumma Rabbana wa lakal-hamd (O Allah, our Lord and to You be the praise).'"
Reference : Sunan an-Nasa'i 1060In-book reference : Book 12, Hadith 32English translation : Vol. 2, Book 12, Hadith 1061