It is narrated from Ubaid bin Umair, may Allah have mercy on him, who states: A trustworthy person informed me (as if he meant Aisha, may Allah be pleased with her). Then he mentioned the prayer of the Prophet ﷺ and that Abu Bakr, may Allah be pleased with him, was at his side, similar to the narration of Hisham bin Urwah from his father.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 316
Hadith Takhrijصحیح من غیر ہذا الطریق کما تقدم، اخرجہ البئیقی فی معرفة السنن والآثار: 1465