Sahih Bukhari Volume 002, Book 022, Hadith Number 297A.
Narated By Anas bin Malik : While Abu Bakr was leading the people in the morning prayer on a Monday, the Prophet came towards them suddenly having lifted the curtain of 'Aisha's house, and looked at them as they were standing in rows and smiled. Abu Bakr tried to come back thinking that Allah's Apostle wanted to come out for the prayer. The attention of the Muslims was diverted from the prayer because they were delighted to see the Prophet. The Prophet waved his hand to them to complete their prayer, then he went back into the room and let down the curtain. The Prophet expired on that very day.