قَالَ مَالِك : وَلَا بَأْسَ أَنْ يَشْتَرِيَ الرَّقَبَةَ فِي التَّطَوُّعِ، وَيَشْتَرِطَ أَنْ يُعْتِقَهَا .
Imam Malik, may Allah have mercy on him, said: If someone wishes to free a slave voluntarily, he may do so by stipulating the condition of freedom.