Bilal called the iqamah for the prayer. Abu Bakr stepped forward and began to lead the prayer. Then the Prophet ﷺ arrived, walking through the rows, parting them until he stood in the first row. The people began clapping.Sahl said, "Do you know what tasfeeh is? It is clapping."Abu Bakr would not turn around during his prayer, but when their clapping increased he looked back and saw the Prophet ﷺ in the row. The Prophet ﷺ gestured to him to stay in his place. Abu Bakr raised his hands, praised Allah, then stepped backward in retreat, and the Prophet ﷺ moved forward and led the prayer.
أقام بلال الصلاة. فتقدم أبو بكر فصلي، فجاء النبي ﷺ يمشي في الصفوف يشقها شقا حتى قام في الصف الأول. فأخذ الناس بالتصفيح قال سهل: هل تدرون ما التصفيح؟ هو التصفيق. وكان أبو بكرضي الله عنه لا يلتفت في صلاته، فلما أكثروا التفت، فإذا النبي ﷺ في الصف فأشار إليه: مكانك فرفع أبو بكر يديه، فحمد الله، ثم رجع القهقرى وراءه، وتقدم النبي ﷺ فصلى.
Bukhari narrated it in the Book of Actions During Prayer (1201), and Muslim in the Book of Prayer (103/421), both from the hadith of Abdul-Aziz bin Abu Hazim, from his father, from Sahl bin Saad, and the wording given here is Bukhari's. Its chain has already been discussed in the chapters on leading the prayer.This hadith shows that minor movement during prayer is permissible, since Abu Bakr stepped back from his position to the row behind him, and that anyone who needs to do something similar should step backward rather than turn his back on the qibla or turn away from it.