In his pledge that they do not flee.

Aḥmad b. ʿAbdullāh > Layth b. Saʿd > Abū al-Zubayr > Jābir b. ʿAbdullāh

We were one thousand and four hundred on the Day of Hudaibiya. We swore fealty to hiin (the Holy Prophet) and 'Umar was holding the latter's hand (when he was sitting) under the tree (called) Samura (to administer the oath to the Companions). The narrator added: We took oath to the effect that we would not flee (from the battlefield if there was an encounter with the Meccans), but we did not take oath to fight to death. – Sound Chain

أَخْبَرَنَا أَحْمَدُ بْنُ عَبْدِ اللَّهِ حَدَّثَنَا لَيْثُ بْنُ سَعْدٍ عَنْ أَبِي الزُّبَيْرِ عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ

أَنَّهُ قَالَ كُنَّا يَوْمَ الْحُدَيْبِيَةِ أَلْفًا وَأَرْبَعَ مِائَةٍ فَبَايَعْنَاهُ وَعُمَرُ آخِذٌ بِيَدِهِ تَحْتَ الشَّجَرَةِ وَهِيَ سَمُرَةٌ وَقَالَ «بَايَعْنَاهُ عَلَى أَنْ لَا نَفِرَّ وَلَمْ نُبَايِعْهُ عَلَى الْمَوْتِ» – إسناده صحيح