2 Liberty can be left to a slave by a trust charging an heir, legatee, or other person already benefited by a trust of the testator's, with his manumission, and it makes no difference whether the slave is the property of the testator, of the heir, of the legatee or of a stranger: for a stranger's slave must be purchased and manumitted; and on his master's refusal to sell (which refusal is allowable only if the master has taken nothing under the will) the trust to enfranchise the slave is not extinguished, as though its execution had become impossible, but its execution is merely postponed; because it may become possible to free him at some future time, whenever an opportunity of purchasing him presents itself. A trust of manumission makes the slave the freedman, not of the testator, though he may have been his owner, but of the manumitter, whereas a direct bequest of liberty makes a slave the freedman of the testator, whence too he is called 'orcinus.' But a direct bequest of liberty can be made only to a slave who belongs to the testator both at the time of making his will and at that of his decease; and by a direct bequest of liberty is to be understood the case where the testator desires him to become free in virtue, as it were, of his own testament alone, and so does not ask some one else to manumit him. 3 The words most commonly used to create a trust are I beg, I. request, I wish, I commission, I trust to your good faith; and they are just as binding when used separately as when united. TITLE XXV. OF CODICILS It is certain that codicils were not in use before the time of Augustus, for Lucius Lentulus, who was also the originator of trusts, was the first to introduce them, in the following manner. Being on the point of death in Africa, he executed codicils, confirmed by his will, by which he begged Augustus to do something for him as a trust; and on the Emperor's fulfilling his wishes, other persons followed the precedent and discharged trusts created in this manner, and the daughter of Lentulus paid legacies which could not have been legally claimed from her. It is said that Augustus called a council of certain jurists, among them Trebatius, who at that time enjoyed the highest reputation, and asked them whether the new usage could be sanctioned, or did not rather run counter to the received principles of law, and that Trebatius recommended their admission, remarking 'how convenient and even necessary the practice was to citizens,' owing to the length of the journeys which were taken in those early days, and upon which a man might often be able to make codicils when he could not make a will. And subsequently, after codicils had been made by Labeo, nobody doubted their complete validity.