Such authority, for instance, is not necessary when a pupil stipulates for the delivery of property, though it is otherwise where he is the promisor; for it is an established rule that the guardian's authority is not necessary for any act by which the pupil simply improves his own position, though it cannot be dispensed with where he proposes to make it worse.
"The Institutes of Justinian"
Caesar Flavius Justinian
Conversely, a stipulation which originally was perfectly good may be avoided by the thing, which is its object, acquiring any of the characters just specified through no fault of the promisor.
"The Institutes of Justinian"
Caesar Flavius Justinian
13 Formerly, a man could not stipulate that a thing should be conveyed to him after his own death, or after that of the promisor; nor could one person who was in another's power even stipulate for conveyance after that person's death, because he was deemed to speak with the voice of his parent or master; and stipulations for conveyance the day before the promisee's or promisor's decease were also void.
"The Institutes of Justinian"
Caesar Flavius Justinian