The Imam is appointed to be followed. So recite takbir when he recites it, and bow down when he bows down and when he utters:" Allah listens to him who praises Him," say" O Allah, our Lord, for Thee be the praise." And when he prays, standing, you should pray standing. And when he prays sitting, all of you should pray sitting.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ إِنَّمَا جُعِلَ الإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا اللَّهُمَّ رَبَّنَا لَكَ الْحَمْدُ وَإِذَا صَلَّى قَائِمًا فَصَلُّوا قِيَامًا وَإِذَا صَلَّى قَاعِدًا فَصَلُّوا قُعُودًا أَجْمَعُونَ  

[Machine] Abu Hurairah narrated that the Prophet Muhammad ﷺ said: "Whoever obeys me has indeed obeyed Allah, and whoever disobeys me has indeed disobeyed Allah. Whoever obeys the leader has indeed obeyed me, for the leader is like a fortress. If someone prays while sitting, then everyone should pray sitting or kneeling. When he says 'Sami Allahu liman hamidah' (Allah hears whoever praises Him), then say 'Rabbana lakal hamd' (Our Lord, praise is for You). For when the saying of the people of the earth coincides with the saying of the people of the heavens, his previous sins will be forgiven."  

حَدَّثَنِي أَبُو هُرَيْرَةَ مِنْ فِيهِ إِلَى فِي قَالَ سَمِعْتُ رَسُولَ اللهِ ﷺيَقُولُ مَنْ أَطَاعَنِي فَقَدْ أَطَاعَ اللهَ وَمَنْ عَصَانِي فَقَدْ عَصَى اللهَ وَمَنْ أَطَاعَ الْأَمِيرَ فَقَدْ أَطَاعَنِي إِنَّمَا الْأَمِيرُ مِجَنٌّ فَإِنْ صَلَّى جَالِسًا فَصَلُّوا جُلُوسًا أَوْ قُعُودًا فَإِذَا قَالَ سَمِعَ اللهُ لِمَنْ حَمِدَهُ فَقُولُوا اللهُمَّ رَبَّنَا لَكَ الْحَمْدُ فَإِنَّهُ إِذَا وَافَقَ قَوْلُ أَهْلِ الْأَرْضِ قَوْلَ أَهْلِ السَّمَاءِ غُفِرَ لَهُ مَا مَضَى مِنْ ذَنْبِهِ  

Messenger of Allah ﷺ said, "Whoever obeys me, obeys Allah, and whoever disobeys me, disobeys Allah, and whoever obeys the ruler I appoint, obeys me, and whoever disobeys him, disobeys me." (Using translation from Bukhārī 7137)  

سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ مَنْ أَطَاعَنِي فَقَدْ أَطَاعَ اللهَ وَمَنْ عَصَانِي فَقَدْ عَصَى اللهَ وَمَنْ أَطَاعَ الْأَمِيرَ فَقَدْ أَطَاعَنِي وَمَنْ عَصَى الْأَمِيرَ فَقَدْ عَصَانِي إِنَّمَا الْإِمَامُ جُنَّةٌ فَإِنْ صَلَّى قَاعِدًا فَصَلُّوا قُعُودًا وَإِذَا قَالَ سَمِعَ اللهُ لِمَنْحَمِدَهُ فَقُولُوا اللهُمَّ رَبَّنَا وَلَكَ الْحَمْدُ فَإِذَا وَافَقَ قَوْلُ أَهْلِ الْأَرْضِ قَوْلَ أَهْلِ السَّمَاءِ غُفِرَ لَهُ مَا مَضَى مِنْ ذَنْبِهِ  

“The Messenger of Allah ﷺ said: ‘The Imam is appointed to be followed. When he says Allahu Akbar, then say Allahu Akbar; when he bows, then bow; when he says Sami’ Allahu liman hamidah, then say Rabbana wa lakal-hamd; when he prostrates then prostrate; if he prays standing, then pray standing, and if he prays sitting down then pray sitting down.” (Using translation from Ibn Mājah 1239)   

أَنَّ النَّبِيَّ ﷺ قَالَ «إِنَّمَا جُعِلَ الْإِمَامُ لِيُؤْتَمَّ بِهِ فَلَا تَخْتَلِفُوا عَلَيْهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا اللَّهُمَّ رَبَّنَا لَكَ الْحَمْدُ وَإِذَا صَلَّى قَاعِدًا فَصَلُّوا قُعُودًا أَجْمَعُونَ»  

The Imam is appointed to be followed. So recite takbir when he recites it, and bow down when he bows down and when he utters:" Allah listens to him who praises Him," say" O Allah, our Lord, for Thee be the praise." And when he prays, standing, you should pray standing. And when he prays sitting, all of you should pray sitting. (Using translation from Muslim 417)  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «إِنَّمَا الْإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا رَفَعَ فَارْفَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ فَقُولُوا اللَّهُمَّ رَبَّنَا لَكَ الْحَمْدُ وَإِذَا صَلَّى قَائِمًا فَصَلُّوا قِيَامًا وَإِذَا صَلَّى قَاعِدًا فَصَلُّوا قُعُودًا أَجْمَعُونَ»