Anas bin Malik reported,

While the Muslims were performing the Fajr prayer on Monday with Abu Bakr رضي الله عنه leading them, the Prophet ﷺ suddenly drew back the curtain of Ayesha's chamber رضي الله عنها and looked out at them as they stood in rows. He smiled and laughed.Abu Bakr رضي الله عنه stepped back on his heels, thinking that the Messenger of Allah ﷺ intended to come out for the prayer. The Muslims were nearly distracted from their prayer out of joy at seeing the Prophet ﷺ. But he gestured with his hand for them to complete their prayer, then entered the chamber and let down the curtain. He passed away that same day.

Bukhari 1205

Sahih

حدثنا بشر بن محمد أخبرنا عبد الله قال يونس قال الزهري أخبرني

أنس بن مالك

أن المسلمين بينا هم في الفجر يوم الاثنين وأبو بكر رضي الله عنه يصلي بهم ففجئهم النبي ﷺ قد كشف ستر حجرة عائشة رضي الله عنها فنظر إليهم وهم صفوف فتبسم يضحك فنكص أبو بكر رضي الله عنه على عقبيه وظن أن رسول الله ﷺ يريد أن يخرج إلى الصلاة وهم المسلمون أن يفتتنوا في صلاتهم فرحا بالنبي ﷺ حين رأوه فأشار بيده أن أتموا ثم دخل الحجرة وأرخى الستر وتوفي ذلك اليوم

البخاري 1205صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Work during prayer
Chapter
One who steps backward or forward in prayer due to something that befalls him
Numbering
Darussalam 1205
Bukhari 1205