Anas bin Malik reported,

The Prophet ﷺ fell from a horse and scraped his right side. We went to visit him, and when the time for prayer came, he led us in prayer while sitting, so we prayed behind him sitting as well.When he finished the prayer, he said, "The imam is appointed only to be followed. When he says the takbir, say the takbir. When he prostrates, prostrate. When he rises, rise. When he says, 'Allah hears whoever praises Him,' say, 'Our Lord, to You belongs all praise.' And when he prays sitting, all of you pray sitting."

Azami 2074

Sahih

عن أنس بن مالك يقول

سقط النبي ﷺ عن فرس فجحش شقه الأيمن، فدخلنا عليه، نعوده، فحضرت الصلاة، فصلى بنا قاعدا. فصلينا وراءه قعودا، فلما قضى الصلاة قال: إنما جعل الإمام ليؤتم به، فإذا كبر فكبروا، وإذا سجد فاسجدوا، وإذا رفع فارفعوا، وإذا قال: سمع الله لمن حمده فقولوا ربنا ولك الحمد، وإذا صلى قاعدا فصلوا قعودا أجمعون.

الأعظمي 2074صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Prayer
Chapter
Ruku and sujud
Section
Imam saying "Allah hears the one who praises Him"
Numbering
Jami al-Kamil 2074 (2nd edition)
Azami 2074