حَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم صُرِعَ عَنْ فَرَسٍ فَجُحِشَ شِقُّهُ الأَيْمَنُ بِنَحْوِ حَدِيثِهِمَا وَزَادَ ‏"‏ فَإِذَا صَلَّى قَائِمًا فَصَلُّوا قِيَامًا ‏"‏ ‏.‏

Anas b. Malik reported: The Messenger of Allah (PBUH) fell down from a horse and his right side was grazed, and the rest of the hadith is the same with the addition of these words:" When he (the Imam) says prayer standing, you should also do so." Translation Not Available

Book Ref: Sahih Muslim Book 4 Hadith 819
Web Ref:  Sahih Muslim Book 4 Hadith 411 c