"I formed a partnership with 'Ammar and Sa'd on the day of Badr. Sa'd brought two prisoners but 'Ammar and I did not bring anything." (Using translation from Nasāʾī 3937)  

«اشْتَرَكْتُ أَنَا وَعَمَّارٌ وَسَعْدٌ يَوْمَ بَدْرٍ فَجَاءَ سَعْدٌ بِأَسِيرَيْنِ وَلَمْ أَجِيءْ أَنَا وَعَمَّارٌ بِشَيْءٍ»  

[Machine] It is permissible if they both agree for one of them to decide over the other.  

جَائِزٌ إِذَا كَانَا مُتَفَاوِضَيْنِ يَقْضِي أَحَدُهُمَا عَلَى الْآخَرِ