The Prophet ﷺ came to know that one of his companions had given the promise of freeing his slave after his death, but as he had no other property than that slave, the Prophet ﷺ sold that slave for 800 dirhams and sent the price to him.  

بَلَغَ النَّبِيَّ ﷺ أَنَّ رَجُلاً مِنْ أَصْحَابِهِ أَعْتَقَ غُلاَمًا عَنْ دُبُرٍ لَمْ يَكُنْ لَهُ مَالٌ غَيْرَهُ فَبَاعَهُ بِثَمَانِمِائَةِ دِرْهَمٍ ثُمَّ أَرْسَلَ بِثَمَنِهِ إِلَيْهِ