From Sahih Bukhari (Hadith 683):
Narrated Hisham ibn `Urwa's father:`Aisha said, "Allah's Messenger (ﷺ) ordered Abu Bakr to lead the people in the prayer during his illness and so he led them in prayer." `Urwa, a sub narrator, added, "Allah's Messenger (ﷺ) felt a bit relieved and came out and Abu Bakr was leading the people. When Abu Bakr saw the Prophet (ﷺ) he retreated but the Prophet beckoned him to remain there. Allah's Messenger (ﷺ) sat beside Abu Bakr. Abu Bakr was following the prayer of Allah's Messenger (ﷺ) and the people were following the prayer of Abu Bakr
Reference: Bukhari 683