Digestorum libri
Ex libro XXIII
Dig. 40,1,15Marcellus libro vicensimo tertio digestorum. Mortis causa servum manumitti posse non est dubitandum. quod non ita tibi intellegendum est, ut ita liber esse iubeatur, ut, si convaluerit dominus, non fiat liber, sed quemadmodum si vindicta eum liberaret absolute, scilicet quia moriturum se putet, mors eius exspectabitur, similiter et in hac specie in extremum tempus manumissoris vitae confertur libertas, durante scilicet propter mortis causae tacitam condicionem) voluntate manumissoris: quemadmodum cum rem ita tradiderit, ut moriente eo fieret accipientis, quae ita demum alienatur, si donator in eadem permanserit voluntate.
Marcellus, Digest, Book XXIII. There is no doubt that a slave can be manumitted mortis causa. You must not, however, understand if a slave is ordered to be free in this manner that he will not become so if his master should recover his health; for just as if he had been absolutely manumitted before the Prætor, when anyone thinks that he is about to die, and his death is expected, so, in this instance, freedom is granted during the last moments of the person who bestows the manumission, as his will is considered to continue to exist on account of the tacit condition of the death of the person manumitting the slave. The case is the same as if someone should deliver property under the condition that, if he dies, it shall belong to the person who receives it; since the property will not be alienated if the donor retains the same intention during his lifetime.