Sahih al-Bukhari 811

Arabic

حَدَّثَنَا آدَمُ، حَدَّثَنَا إِسْرَائِيلُ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَبْدِ اللَّهِ بْنِ يَزِيدَ الْخَطْمِيِّ، حَدَّثَنَا الْبَرَاءُ بْنُ عَازِبٍ ـ وَهْوَ غَيْرُ كَذُوبٍ ـ قَالَ كُنَّا نُصَلِّي خَلْفَ النَّبِيِّ صلى الله عليه وسلم فَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ‏.‏ لَمْ يَحْنِ أَحَدٌ مِنَّا ظَهْرَهُ حَتَّى يَضَعَ النَّبِيُّ صلى الله عليه وسلم جَبْهَتَهُ عَلَى الأَرْضِ‏.‏

English translation

Narrated Al-Bara' bin `Azib:(He was not a liar) We used to pray behind the Prophet (ﷺ) and when he said, "Sami`a l-lahu liman hamidah", none of us would bend his back (to go for prostration) till the Prophet (ﷺ) had placed his, forehead on the ground

Reference: Sahih al-Bukhari 811, Book of Call to Prayers (Adhaan). English translation by Dr. Muhammad Muhsin Khan.