question #1 Sahih Muslim 411d, Book 4, Hadith 86 : What should be the posture of a follower during prayer when the Imam is in an erect posture?

The Messenger of Allah (ﷺ) rode a horse and fell down from it and his right side was grazed, and the rest of the hadith is the same, and (these words) are found in it:” When he (the Imam) says prayer in an erect posture, you should also say it in an erect posture.”