Sahih Muslim 1944
صحيح مسلم#1944Sahihوَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا يَحْيَى بْنُ آدَمَ، عَنْ سُفْيَانَ، عَنْ مُوسَى بْنِ، عُقْبَةَ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ صَلَّى رَسُولُ اللَّهِ صلى الله عليه وسلم صَلاَةَ الْخَوْفِ فِي بَعْضِ أَيَّامِهِ فَقَامَتْ طَائِفَةٌ مَعَهُ وَطَائِفَةٌ بِإِزَاءِ الْعَدُوِّ فَصَلَّى بِالَّذِينَ مَعَهُ رَكْعَةً ثُمَّ ذَهَبُوا وَجَاءَ الآخَرُونَ فَصَلَّى بِهِمْ رَكْعَةً ثُمَّ قَضَتِ الطَّائِفَتَانِ رَكْعَةً رَكْعَةً - قَالَ - وَقَالَ ابْنُ عُمَرَ فَإِذَا كَانَ خَوْفٌ أَكْثَرَ مِنْ ذَلِكَ فَصَلِّ رَاكِبًا أَوْ قَائِمًا تُومِئُ إِيمَاءً .
Ibn Umar reported that the Messenger of Allah (ﷺ) observed prayer in danger on some day (in this way):a group stood with him (the Holy Prophet) (for prayer) and the other group stood In front of the enemy. Then those who were with (him) observed one rak'ah of prayer and they went back and the others came and they observed one rak'ah (with him). Then both the groups completed one rak'ah each. Ibn Umar said: When there is greater danger, then observe prayer even on the ride or with the help of gestures in a standing posture
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 6:372