Sahih Muslim Book 4, Hadith 111
The Messenger of Allah (ﷺ) went to the tribe of Bani Amr b. Auf in order to bring reconciliation amongst (its members), and It was a time of prayer. The Mu'adhdhin came to Abu Bakr and said: Would you lead the prayer in case I recite takbir (tahrima, with which the prayer begins)? He (Abu Bakr) said: Yes. He (the narrator) said: He (Abu Bakr) started (leading) the prayer. The people were engaged in observing prayer when the Messenger of Allah (ﷺ) happened to come there and made his way (through the people) till he stood in a row. The people began to clap (their hands), but Abu Bakr paid no heed (to it) in prayer. When the people clapped more vigorously, he (Abu Bakr) then paid heed and saw the Messenger of Allah (ﷺ) there. (He was about to withdraw when) the Messenger of Allah (ﷺ) signed to him to keep standing at his place. Abu Bakr lifted his hands and praised Allah for what the Messenger of Allah (ﷺ) had commanded him and then Abu Bakr withdrew himself till he stood in the midst of the row and the Messenger of Allah (ﷺ) stepped forward and led the prayer. When (the prayer) was over, he (the Holy Prophet) said: 0 Abu Bakr, what prevented you from standing (at that place) as I ordered you to do? Abu Bakr said: It does not become the son of Abu Quhafa to lead prayer before the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) said (to the people) around him: What is it that I saw you clapping so vigorously? (Behold) when anything happens in prayer, say: Subha Allah, for when you would utter it, it would attract the attention, while clapping of hands is meant for women.
When the Messenger of Allah (ﷺ) became ill and illness became serious he ordered Abu Bakr to lead the people in prayer. Upon this 'A'isha said: Messenger of Allah, Abd Bakr is a man of tenderly feelings: when he would stand in your place (he would be so much overwhelmed -by grief that) he would not be able to lead the people in prayer. He (the Holy Prophet) said: You order Abu Bakr to lead the people in prayer, and added: You are like the female companions of Yusuf. So Abu Bakr led the prayer (during this period of illness) in the life of the Messenger of Allah (ﷺ).
" Abu Bakr lifted his hands and praised Allah and retraced his (steps) till he stood in a row."