Muwatta Imam Malik (Riwayat Yahya)

Imam Malik, may Allah have mercy on him, said: If someone makes a bequest of one-third of his wealth to a person, and says, "My slave should serve such-and-such person as long as that person is alive, then he is free," and afterwards the value of the slave equals one-third of the wealth, then the value of the slave's service will be assessed, and shares will be divided in the slave. The one to whom the bequest of one-third was made will have a share of one-third, and the one to whom the service was bequeathed will have a share according to the service. After that, both persons will take their share from the service or earnings of the slave. When the person for whom the service was intended dies, the slave will become free.