Hadithcore
Mishkat al-Masabih, 857

Abu Huraira reported God’s Messenger as saying, “The <i>imam</i> is appointed only to be followed, so when he says the <i>takbir</i>, say it also; and when he recites, listen silently.” Abu Dawud, Nasa’i and Ibn Majah transmitted it.

وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِنَّمَا جُعِلَ الْإِمَامُ لِيُؤْتَمَّ بِهِ فَإِذَا كَبَّرَ فَكَبِّرُوا وَإِذَا قَرَأَ فَأَنْصِتُوا» . رَوَاهُ أَبُو دَاوُد وَالنَّسَائِيّ وَابْن مَاجَه

References1 variant
In-Book Reference
Book 4, Hadith 281