Sunan An Nasai 3970

أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَنْبَأَنَا ابْنُ الْمُبَارَكِ، ‏‏‏‏‏‏عَنْ يُونُسَ، ‏‏‏‏‏‏عَنِ الزُّهْرِيِّ، ‏‏‏‏‏‏فِي عَبْدَيْنِ مُتَفَاوِضَيْنِ كَاتَبَ أَحَدُهُمَا، ‏‏‏‏‏‏قَالَ:‏‏‏‏ جَائِزٌ إِذَا كَانَا مُتَفَاوِضَيْنِ يَقْضِي أَحَدُهُمَا عَنِ الْآخَرِ .

It was narrated from Az-Zuhri concerning two slaves who were partners, and one of them quit, that he said: One of them may cover for the other if they were partners.