Abdullah bin Abbas reported,

The Prophet ﷺ stood up and the people stood with him. He said the takbir and they said it with him. He bowed, and some of them bowed with him. Then he prostrated and they prostrated with him. Then he stood for the second rakah, and those who had prostrated with him stood up and guarded their brothers, while the other group came forward, bowed, and prostrated with him. All the people were in prayer, but they were guarding one another.

Bukhari 944

Sahih

حدثنا حيوة بن شريح قال حدثنا محمد بن حرب عن الزبيدي عن الزهري عن عبيد الله بن عبد الله بن عتبة

عن ابن عباس رضي الله عنهما قال

قام النبي ﷺ وقام الناس معه فكبر وكبروا معه وركع وركع ناس منهم معه ثم سجد وسجدوا معه ثم قام للثانية فقام الذين سجدوا وحرسوا إخوانهم وأتت الطائفة الأخرى فركعوا وسجدوا معه والناس كلهم في صلاة ولكن يحرس بعضهم بعضا

البخاري 944صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Prayer of fear
Chapter
Guarding one another during the fear prayer
Numbering
Darussalam 944
Bukhari 944