Responsa על שבועות 82:3

Q. A summoned his father-in-law, B, to court and claimed: 1) that B's father-in-law, C, (A's grandfather), bequeathed twenty-five marks to B's two daughters with the provision that if one daughter died childless, the other should inherit her part, and if the second daughter likewise died childless, the twenty-five marks were to go to C's male heirs; 2) that the money was deposited with B; and 3) that after he, A, had been married to B's daughter for two years, the other daughter died while still a minor. A, therefore, demanded the twenty-five marks from B. B, on the other hand, claimed that he had given the twenty-five marks to A as dowry upon the latter's marriage to his daughter. A, however, claimed that upon receiving his dowry he was not told about the twenty-five marks and that B could not have given him that money since the younger daughter was still alive. To this claim B answered that he expected to give his own money to his younger daughter. He further claims that A's wife has no children yet and, therefore, he, B, cannot give anything to A since in case A's wife dies childless, C's heirs will keep him responsible for the money.
A. B is under no obligation to A for the following reasons: 1) We believe B's claim that he included the money of his departed daughter in A's dowry, since B could have claimed that his younger daughter gave him her money, and this latter claim would have been irrefutable; 2) the father is the rightful heir of the departed daughter since C's provision for the disposition of his gift in case the daughter die childless is void.
Q. A claims that he has witnesses who will testify that B took from his (A's) father thirty marks. B claims that he returned to A whatever he had taken from his father.
A. If the witnesses will testify that B robbed A's father, A should take an oath that B did not as yet return the money to him, and be entitled to collect the thirty marks from B. If, however, B received the money from A's father in a legitimate way, B should take an oath that he had paid all the money he owed to his father, and be free from obligation.
SOURCES: Cr. 283–4; Pr. 1017; Mordecai Hagadol, p. 227a.