Responsa for Bava Metzia 132:28

Q. A sold his house to B and undertook to settle with the abutter so that the latter would not take the house away from B. The abutter, also, told B that having no money he did not want to buy the house. B, however, failed to bind the abutter by a kinyan. A borrowed jewelry from his wife and deposited it with C stating: take formal possession of this jewelry on condition that if I fail to settle with the abutter it will belong to B from now on. B, on the other hand, deposited twenty^*Cr. reads: “two;” Mord. reads: “four;” L. and Tesh. Maim. read: “twenty.” marks with C as a guaranty that he would pay the price of the house and that he would not change his mind. After the transaction was concluded, however, the abutter obtained money, paid off B, and took away the house; B, therefore, demanded of C that he turn over to him the valuables A had deposited with him. C told A in the presence of witnesses of B's demand and A replied that he should give the valuables to B "since it is legally coming to him". Is B entitled to the valuables?
A. A gave the valuables to C in order that he deliver them to B should a certain condition not be fulfilled. Such a transaction is called asmakhta and is not binding since it was not made before an authoritative court. When A finally told C to deliver the valuables to B, he was acting under misapprehension that they were due him legally, as his statement indicates. His order, therefore, was not binding and B should return the valuables to A.
SOURCES: Cr. 290; L. 309; Mord. B. B. 324; Tesh. Maim to Kinyan, 3.

Q. A bought silver from B. Having no money to pay for it, he gave B a quantity of gold on condition that should he fail to pay B within three days, B would have the right to raise money against such gold by using it as security on an interest-bearing loan, or by having the money-changers exchange it for money, or by resorting to any other possible manner of raising money. B, however, pledged the gold with C on condition that it become forfeited after two weeks shall have elapsed, should A fail to redeem it within that time. A did not redeem his gold within the stipulated time. Now A demands that B return his gold since he never intended to allow B to pledge his gold on such unusual, and extremely unfavorable, conditions. By the phrase "any other possible manner" he meant to permit the employment of customary methods of raising money against security, and no more. Moreover, B did not necessarily have to raise a loan. He could have taken off a piece of the gold commensurate in value with the money due him, and returned the remainder to A; since gold bullion lends itself to such treatment without the necessity of appraisal [by a court]. B, on the other hand, claims that knowing what a dilatory debtor A was, he refused to do business with him until A gave him the gold and specified that it could be used to raise money "in any possible manner", the last phrase to be taken literally. He further claims that he could not raise the money in any other way than on the terms made with C, and that he informed A about this transaction with C, and that A agreed to it. A, however, denies B's assertions and claims that he was informed of the transaction with C after he had mounted his horse and had been ready to ride on his way, and that he did not realize at the time the meaning of B's words.
A. Even assuming the truth of B's version of his agreement with A, such agreement is considered an asmakhta and is not valid unless accompanied by a kinyan and made before an authoritative court. Therefore, B must pay to A the difference between the value of A's gold and the amount due B. Moreover, B's agreement with C regarding the forfeiture of the pledge is also considered an askmakhta and is invalid.
SOURCES: Cr. 170; L. 331.