Sunan Abi Dawud 622
Al-Bara (b. Azib)said; They (the Companions) used to pray along with the Messenger of Allah (ﷺ). When he bowed, they  bowed; and when he said, “Allah listens to him who praises him”, they remained standing until they saw that he placed his placed his forehead on the ground:
then they would follow him (ﷺ)
حَدَّثَنَا الرَّبِيعُ بْنُ نَافِعٍ، حَدَّثَنَا أَبُو إِسْحَاقَ، - يَعْنِي الْفَزَارِيَّ - عَنْ أَبِي إِسْحَاقَ، عَنْ مُحَارِبِ بْنِ دِثَارٍ، قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ يَزِيدَ، يَقُولُ عَلَى الْمِنْبَرِ حَدَّثَنِي الْبَرَاءُ، أَنَّهُمْ كَانُوا يُصَلُّونَ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَإِذَا رَكَعَ رَكَعُوا وَإِذَا قَالَ ‏
"‏ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ ‏"‏ ‏.‏ لَمْ نَزَلْ قِيَامًا حَتَّى يَرَوْهُ قَدْ وَضَعَ جَبْهَتَهُ بِالأَرْضِ ثُمَّ يَتَّبِعُونَهُ صلى الله عليه وسلم ‏.‏