Hadith 1060
Chapter 21: What the Imam says when he raises his head from bowing - كتاب التطبيق
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 1060
In-book reference : Book 12, Hadith 32