They used to say prayer behind the Messenger of Allah ﷺ. I never saw anyone bending his back at the time when he (the Holy Prophet) raised his head, till the Messenger of Allah ﷺ placed his forehead on the ground. They then fell in prostration after him.
حَدَّثَنِي الْبَرَاءُ وَهُوَ غَيْرُ كَذُوبٍ أَنَّهُمْ كَانُوا يُصَلُّونَ خَلْفَ رَسُولِ اللَّهِ ﷺ فَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ لَمْ أَرَ أَحَدًا يَحْنِي ظَهْرَهُ حَتَّى يَضَعَ رَسُولُ اللَّهِ ﷺ جَبْهَتَهُ عَلَى الأَرْضِ ثُمَّ يَخِرُّ مَنْ وَرَاءَهُ سُجَّدًا