Sunan an-Nasai 15842
In-book no 1106أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ الْمَرْوَزِيُّ، قَالَ أَنْبَأَنَا شَرِيكٌ، عَنْ أَبِي إِسْحَاقَ، قَالَ وَصَفَ لَنَا الْبَرَاءُ السُّجُودَ فَوَضَعَ يَدَيْهِ بِالأَرْضِ وَرَفَعَ عَجِيزَتَهُ وَقَالَ هَكَذَا رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَفْعَلُ .
It was narrated that Abu Ishaq said: "Al-Bara' described the prostration to us. He places his hands on the ground and raised his posterior and said: 'This is what I saw the Messenger of Allah (ﷺ) doing."