Responsa for Ketubot 163:15

Q - A negotiated a marriage between his son C, and B's daughter L. A deposited a pledge with D on condition that should C fail to marry L, by a certain date, D should give the pledge to B, This conditional transaction was accompanied by a kinyan (a symbolic act which makes an agreement binding) made before an authoritative court, effective as of now. A died prior to that specified date and C failed to marry L. Is the pledge awarded to B?
This question was apparently also asked by R. Mordecai.
A - The pledge is not awarded to B and the agreement is voided because: (1) conditional transactions classified as asmakhta, (a conditional stipulation in a verbal or written contract, providing for the payment of a fine in case of nonfulfillment of a promise)that were made before an authoritative court are invalid, in cases where one is prevented by unavoidable accident, from carrying out his part of the agreement. Death most certainly constitutes an unavoidable accident. (2) The kinyan did not terminate during A's lifetime, for it commenced when A deposited the pledge with D, and was to conclude at the expiration of the specified date. (3) Terms of a stipulation that were not completed by A during his lifetime, have no effect, in regard to his son C. A son is obligated to carry out his late father's directives in matters of giving presents etc. to others, but not in cases of asmakhta that were accompanied by an unavoidable accident. Although the Geonim dealt harshly with the party who retracted the arrangements preliminary to betrothal, and held him monetarily responsible. for the embarrassment which resulted, this is not applicable, in the case of an orphan.