in question and answer, as where it is said, Do you promise? I promise. Will you  give? I will give. Will you do? I will do. Do you guarantee? I guarantee.  Every such stipulation is made absolutely or for a future day or subject to a condition.  Absolutely, as where it is said, Do you promise to give so much money?  without specifying when or under what conditions; the money may be claimed at  once. But if a time is specified at which it ought to be paid, though it is owed at  once it cannot be claimed before the day, nor even on that day, for the debtor  has the whole of it in which to make payment, nor will it be certain that it was  not paid on that day until the whole of the day has passed.15 And in the same way,  16if one has stipulated to pay this year or this month, one will not sue rightfully  unless the whole of the year or month has passed. And so if one stipulates for a  slave or an estate, one cannot properly claim until a time sufficient to make the  transfer has passed.17
If a stipulation is made subject to a condition.
 18A stipulation is sometimes made subject to a condition, as Do you promise to  pay so much money if Titius is made consul?19 And note that in a conditional  stipulation only an expectation is created.2021Conditions which relate to the past  or to the present either immediately invalidate an obligation or are in no way suspensive,  as where it is said if such a one is alive (or has been made consul) do  you promise to give? If the fact is not so, the stipulation is invalid; if it is, the  stipulation is operative at once, for however uncertain we may be about them,  events which by the nature of things are certain do not delay an obligation in any  way.22
Acts as the objects of stipulations.
 23Acts may also be the objects of stipulations, as where a stipulation is made that  something be done or not done; it will there be best to add a penalty lest the value  of the stipulation be uncertain and24 the plaintiff be compelled to prove the extent  of his damage. A penalty may be added in this way, And if this shall not be done,  do you promise to pay so much by way of penalty?2526Places are also a matter  for stipulation, as where you say, [Do you promise to pay at London? But if  you say], being in Exeter, Do you promise to pay today at London? the stipulation  will be void, unless a time is added in which that provided for in the stipulation  may be done, because it will be wholly impossible,2728as though one had  promised a thing which did not or could not exist, or a sacred or public thing which  he is incapable of owning.2930<If the stipulator has one thing in mind and the  promisor another, the stipulation is of no effect, no more than if there had been  no reply to the question.31 Nor is it valid if one stipulates that someone commit  homicide or theft or the like.>3233Nor if one stipulates that another is to give or  do what [the promisor] promises,34 other than one who is in the promisor's potestas,  nor 35if one does not reply to what is asked,
26-27. Inst. 3.15.5: Loca etiam inseri stipulationi solent, veluti Carthagine dare spondes? quae stipulatio, licet pure fieri videtur, tamen re ipsa habet tempus iniectum quo promisor utatur ad pecuniam Carthagine dandam, et ideo si quis ita Romae stipuletur hodie Carthagine dare spondes? inutilis erit stipulatio, cum impossibilis sit repromissio.