صحيح البخاري Sahih Bukhari كتاب الاستسقاء The Book of Al-Istisqa.
بَابُ كَيْفَ حَوَّلَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ظَهْرَهُ إِلَى النَّاسِ:

(17) Chapter. How the Prophet ﷺ turned his back towards the people [while offering the SaIat (prayer) for rain].

1 hadith
Hadith 1025
حَدَّثَنَا آدَمُ ، قَالَ : حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ ، عَنْ الزُّهْرِيِّ ، عَنْ عَبَّادِ بْنِ تَمِيمٍ ، عَنْ عَمِّهِ ، قَالَ : رَأَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَوْمَ خَرَجَ يَسْتَسْقِي ، قَالَ : " فَحَوَّلَ إِلَى النَّاسِ ظَهْرَهُ وَاسْتَقْبَلَ الْقِبْلَةَ يَدْعُو ، ثُمَّ حَوَّلَ رِدَاءَهُ ، ثُمَّ صَلَّى لَنَا رَكْعَتَيْنِ جَهَرَ فِيهِمَا بِالْقِرَاءَةِ " .
Narrated `Abbas bin Tamim from his uncle: "I saw the Prophet on the day when he went out to offer the Istisqa' prayer. He turned his back towards the people and faced the Qibla and asked Allah for rain. Then he turned his cloak inside out and led us in a two rak`at prayer and recited the Qur'an aloud in them."
Hadith Reference Sahih Bukhari / The Book of Al-Istisqa. / Hadith: 1025
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة