Sunan an-Nasai Book 18, Hadith 1540

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَبْدِ الرَّحِيمِ الْبَرْقِيُّ، عَنْ عَبْدِ اللَّهِ بْنِ يُوسُفَ، قَالَ أَنْبَأَنَا سَعِيدُ بْنُ عَبْدِ الْعَزِيزِ، عَنِ الزُّهْرِيِّ، قَالَ كَانَ عَبْدُ اللَّهِ بْنُ عُمَرَ يُحَدِّثُ أَنَّهُ صَلَّى صَلاَةَ الْخَوْفِ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ كَبَّرَ النَّبِيُّ صلى الله عليه وسلم وَصَفَّ خَلْفَهُ طَائِفَةٌ مِنَّا وَأَقْبَلَتْ طَائِفَةٌ عَلَى الْعَدُوِّ فَرَكَعَ بِهِمُ النَّبِيُّ صلى الله عليه وسلم رَكْعَةً وَسَجْدَتَيْنِ ثُمَّ انْصَرَفُوا وَأَقْبَلُوا عَلَى الْعَدُوِّ وَجَاءَتِ الطَّائِفَةُ الأُخْرَى فَصَلُّوا مَعَ النَّبِيِّ صلى الله عليه وسلم فَفَعَلَ مِثْلَ ذَلِكَ ثُمَّ سَلَّمَ ثُمَّ قَامَ كُلُّ رَجُلٍ مِنَ الطَّائِفَتَيْنِ فَصَلَّى لِنَفْسِهِ رَكْعَةً وَسَجْدَتَيْنِ ‏.‏

It was narrated that Az-Zuhri said:"Abdullah bin 'Umar used to narrate that he offered the fear prayer with the Messenger of Allah (ﷺ). He said: 'The Prophet (ﷺ) said the takbir and one group of us formed a row behind him while the other group faced the enemy. The Prophet (ﷺ) led them in bowing once and prostrating twice, then they moved away and faced the enemy, and the other group came and prayed with the Prophet (ﷺ), doing likewise. Then he said the taslim, then each man of both groups stood and prayed by himself, bowing once and prostrating twice