Messenger of Allah ﷺ rode a horse and fell down and the right side of his body was injured. On that day he prayed one of the prayers sitting and we also prayed behind him sitting. When the Prophet ﷺ finished the prayer with Taslim, he said, "The Imam is to be followed and if he prays standing then pray standing, and bow when he bows, and raise your heads when he raises his head; prostrate when he prostrates; and if he says "Samiʿa l-lahu liman hamidah", you should say, "Rabbana wa laka l-hamd.:  

أَنَّ رَسُولَ اللَّهِ ﷺ رَكِبَ فَرَسًا فَجُحِشَ شِقُّهُ الأَيْمَنُ قَالَ أَنَسٌ ؓ فَصَلَّى لَنَا يَوْمَئِذٍ صَلاَةً مِنَ الصَّلَوَاتِ وَهْوَ قَاعِدٌ فَصَلَّيْنَا وَرَاءَهُ قُعُودًا ثُمَّ قَالَ لَمَّا سَلَّمَ إِنَّمَا جُعِلَ الإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا صَلَّى قَائِمًا فَصَلُّوا قِيَامًا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا رَفَعَ فَارْفَعُوا وَإِذَا سَجَدَ فَاسْجُدُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا رَبَّنَا وَلَكَ الْحَمْدُ  

Messenger of Allah ﷺ fell from a horse and got injured so he led the prayer sitting and we also prayed sitting. When he completed the prayer he said, "The Imam is to be followed; if he says Takbir then say Takbir, bow if he bows; raise your heads when he raises his head, when he says, 'Samiʿa l-lahu liman hamidah say, 'Rabbana laka l-hamd', and prostrate when he prostrates."  

أَنَّهُ قَالَ خَرَّ رَسُولُ اللَّهِ ﷺ عَنْ فَرَسٍ فَجُحِشَ فَصَلَّى لَنَا قَاعِدًا فَصَلَّيْنَا مَعَهُ قُعُودًا ثُمَّ انْصَرَفَ فَقَالَ إِنَّمَا الإِمَامُ أَوْ إِنَّمَا جُعِلَ الإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا رَفَعَ فَارْفَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا رَبَّنَا لَكَ الْحَمْدُ وَإِذَا سَجَدَ فَاسْجُدُوا  

The Prophet ﷺ said, "The Imam is to be followed. Say the Takbir when he says it; bow if he bows; if he says 'Samiʿa l-lahu liman hamidah', say, ' Rabbana wa laka l-hamd', prostrate if he prostrates and pray sitting altogether if he prays sitting."  

قَالَ النَّبِيُّ ﷺ إِنَّمَا جُعِلَ الإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا رَبَّنَا وَلَكَ الْحَمْدُ وَإِذَا سَجَدَ فَاسْجُدُوا وَإِذَا صَلَّى جَالِسًا فَصَلُّوا جُلُوسًا أَجْمَعُونَ