Fideicommissorum libri
Ex libro XV
Marcianus, Trusts, Book XV. If the master is ready to alienate the slave, but is not willing to do so before he is satisfied with the price, he ought not to be compelled to liberate him, lest, if he did it, he might obtain little or nothing, if he who is asked to manumit him should prove to be insolvent. 1If the slave does not consent, neither the master nor anyone else should be permitted to proceed with the matter, because a trust of this kind is not one by which anything is acquired by the master; otherwise, the benefit of the trust would appear to accrue only to himself. This might happen if the testator wished the slave to be purchased for more than he was worth, and be manumitted, for then the master could proceed with the execution of the trust; because it would be to his interest to obtain, in addition to the true value of the slave, any excess which the testator ordered to be given him; and it is to the interest of the slave to secure his freedom. 2This will occur where the heir or the legatee is directed to purchase certain property for a special sum of money, and deliver it to another; for then both the owner of the property and the person to whom it is to be delivered can proceed to compel the execution of the trust, as both of them are interested in doing so; the owner, in order that he may obtain any excess over and above the price which the testator has ordered to be given him, and the person to whom the property was left, in order that he may acquire it.
Marcianus, Trusts, Book XV. The opinion of Gaius Cassius is not adopted, for he held that the obligation of manumitting his own slave should not be imposed upon the heir or the legatee, if the services of the slave were so necessary that he could not dispense with them; as, for instance, where he was his steward, or the teacher of children, or where he had committed an unpardonable crime. For the testator is considered to have had these slaves in his power, and the owners have the right to reject the will, but if this is not done, the wishes of the deceased should be carried out.