حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو خَالِدٍ الأَحْمَرُ، عَنِ ابْنِ عَجْلاَنَ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِنَّمَا جُعِلَ الإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا قَرَأَ فَأَنْصِتُوا وَإِذَا قَالَ ‏ Begin hadith 8‏ فَقُولُوا آمِينَ وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا قَالَ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ ‏.‏ فَقُولُوا اللَّهُمَّ رَبَّنَا وَلَكَ الْحَمْدُ وَإِذَا سَجَدَ فَاسْجُدُوا وَإِذَا صَلَّى جَالِسًا فَصَلُّوا جُلُوسًا أَجْمَعِينَ ‏"‏ ‏.‏

It wasnarrated that Abu Hurairah said: “The Messenger of Allah (PBUH)said: ‘The Imam has been appointed to be followed, so when he saysAllahu Akbar, then say Allahu Akbar, when he recites, then listenattentively; when he says: Not (the way) of those who earned Youranger, nor of those who went astray,[1:7] then say Amin; when he bowsthen bow; when he says Sami’ Allahu liman hamidah (Allah hearsthosewho praise Him), then say Allahumma Rabbana wa lakal-hamd (OAllah,our Lord, to You is the praise);” when he prostrates thenprostrate;and if he prays sitting down then all of you pray sittingdown.’” Translation Not Available

Book Ref: Sunan Ibn Majah Book 5 Hadith 846
Web Ref:  Sunan Ibn Majah Vol 1 Book 5 Hadith 846