Sahih al-Bukhari 4561
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · The Statement of Allah the Most High: "...And the Messenger (Muḥammad pbuh) was in your rear calling you back..." (V3:153)
Narrated Al-Bara bin Azib:
حَدَّثَنَا عَمْرُو بْنُ خَالِدٍ ، حَدَّثَنَا زُهَيْرٌ ، حَدَّثَنَا أَبُو إِسْحَاقَ ، قَالَ سَمِعْتُ الْبَرَاءَ بْنَ عَازِبٍ ـ رضى الله عنهما ـ قَالَ جَعَلَ النَّبِيُّ صلى الله عليه وسلم عَلَى الرَّجَّالَةِ يَوْمَ أُحُدٍ عَبْدَ اللَّهِ بْنَ جُبَيْرٍ، وَأَقْبَلُوا مُنْهَزِمِينَ، فَذَاكَ إِذْ يَدْعُوهُمُ الرَّسُولُ فِي أُخْرَاهُمْ، وَلَمْ يَبْقَ مَعَ النَّبِيِّ صلى الله عليه وسلم غَيْرُ اثْنَىْ عَشَرَ رَجُلاً.
The Prophet (ﷺ) appointed `Abdullah bin Jubair as the commander of the infantry during the battle of Uhud. They returned defeated, and that is what is meant by:-- "And the Apostle was calling them back in the rear. None remained with the Prophet (ﷺ) then, but twelve men."