4 It is for the benefit of the principal and a third person when, for instance, some one instructs you to look after affairs common to himself and Titius, or to buy an estate for himself and Titius, or to go surety for them jointly. 5 It is for the benefit of yourself and a third person when, for instance, some one instructs you to lend money at interest to Titius; if it were to lend money free of interest, it would be for the benefit of the third person only. 6 It is for your benefit alone if, for instance, some one commissions you to invest your money in the purchase of land rather than to lend it at interest, or vice versa. But such a commission is not really so much a commission in the eye of the law as a mere piece of advice, and consequently will not give rise to an obligation, for the law holds no one responsible as on agency for mere advice given, even if it turns out ill for the person advised, for every one can find out for himself whether what he is advised to do is likely to turn out well or ill. Consequently, if you have money lying idle in your cashbox, and on so and so's advice buy something with it, or put it out at interest, you cannot sue that person by the action on agency although your purchase or loan turns out a bad speculation; and it has even been questioned, on this principle, whether a man is suable on agency who commissions you to lend money to Titius; but the prevalent opinion is that of Sabinus, that so specific a recommendation is sufficient to support an action, because (without it) you would never have lent your money to Titius at all. 7 So too instructions to commit an unlawful or immoral act do not create a legal obligation--as if Titius were to instigate you to steal, or to do an injury to the property or person of some one else; and even if you act on his instructions, and have to pay a penalty in consequence, you cannot recover its amount from Titius. 8 An agent ought not to exceed the terms of his commission. Thus, if some one commissions you to purchase an estate for him, but not to exceed the price of a hundred aurei, or to go surety for Titius up to that amount, you ought not in either transaction to exceed the sum specified: for otherwise you will not be able to sue him on the agency. Sabinus and Cassius even thought that in such a case you could not successfully sue him even for a hundred aurei, though the leaders of the opposite school differed from them, and the latter opinion is undoubtedly less harsh. If you buy the estate for less, you will have a right of action against him, for a direction to buy an estate for a hundred aurei is regarded as an implied direction to buy, if possible, for a smaller sum. 9 The authority given to an agent duly constituted can be annulled by revocation before he commences to act upon it.