The Book of Prayers (Kitab Al-Salat)

Muslim :: Book 4 : Hadith 820

Anas reported: The Messenger of Allah (may peace be upon him) 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."