Sa'id bin Abi 'Aruba سعيد بن أبي عروبة · The Book of Emancipating Slaves

" If he (one of the joint owners emancipating the slave) has not (enough) money (to secure freedom for the other half) a fair price for the slave should be fixed, and he will be required to work to pay for his freedom, but must not be over-burdened.