Sahih Muslim Book 4, Hadith 87
The Messenger of Allah (ﷺ) fell down from his horse and his right side was grazed, and the rest of the hadith is the same. In this hadith there are no additions (of words) as transmitted by Yunus and Malik.
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."
The Messenger of Allah (ﷺ) fell ill and some of his Companions came to inquire after his health. The Messenger of Allah (ﷺ) said prayer sitting, while (his Companions) said it (behind him) standing. He (the Holy Prophet) directed them by his gesture to sit down, and they sat down (in prayer). After finishing the (prayer) he (the Holy Prophet) said: The Imam is appointed so that he should be followed, so bow down when he bows down, and rise upp when he rises up and say (prayer) sitting when he (the Imam) says (it) sitting.