Arabic (Original)
وَبِإِسْنَادِهِ قَالَ إِذَا كَبَّرَ الْإِمَامُ فَكَبِّرُوا وَإِذَا رَكَعَ فَارْكَعُوا وَإِذَا سَجَدَ فَاسْجُدُوا وَإِنْ صَلَّى جَالِسًا فَصَلُّوا جُلُوسًا.
English Translation
And with the same chain of narration, he said: "When the imam says Allahu Akbar, say Allahu Akbar. When he bows, bow. When he prostrates, prostrate. If he prays sitting, then pray sitting."