Hadith 1509
Chapter 5: The imam turning his back to the people when supplicating during prayers for rain - كتاب الاستسقاء
أَخْبَرَنِي عَمْرُو بْنُ عُثْمَانَ، قَالَ حَدَّثَنَا الْوَلِيدُ، عَنِ ابْنِ أَبِي ذِئْبٍ، عَنِ الزُّهْرِيِّ، عَنْ عَبَّادِ بْنِ تَمِيمٍ، أَنَّ عَمَّهُ، حَدَّثَهُ أَنَّهُ، خَرَجَ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم يَسْتَسْقِي فَحَوَّلَ رِدَاءَهُ وَحَوَّلَ لِلنَّاسِ ظَهْرَهُ وَدَعَا ثُمَّ صَلَّى رَكْعَتَيْنِ فَقَرَأَ فَجَهَرَ .
It was narrated from Abbad bin Tamim that :
His paternal uncle had told him that he went out with the Messenger of Allah (ﷺ) to pray for rain. He turned his rida' around, and turned his back to the people, then he prayed two rak'ahs and recited loudly.
Reference : Sunan an-Nasa'i 1509
In-book reference : Book 17, Hadith 6