Nedarim, Chapter Five, Mishnah Six
This mishnah discusses a subject already dealt with in 4:8, how a person who cannot benefit from another person may nevertheless derive benefit from him by there being a third party intermediary. Our mishnah teaches that when Reuven gives the property to Levi so that Shimon who cannot receive benefit from Reuven, may use the property, the gift needs to be complete. In reality, Levi need not do with the property as Reuven requested. A poignant story shall illustrate this.
1) If one is forbidden by vow to benefit from his neighbor and has nothing to eat, he may give it [the food] to a third party, and he is permitted to use it.
2) It happened to one in Beth Horon that his father was forbidden to benefit from him.
a) Now he [the son] was giving his son in marriage and he said to his neighbor, The courtyard and the banquet are give to you as a gift, but they are yours only that my father may come and feast with us at the banquet.
b) He said to him, If they are mine, let them be dedicated to heaven!
c) [The son] responded, But I did not give you my property to dedicate it to heaven.
d) [The other] responded, You gave me yours so that you and your father might eat and drink together and become reconciled to one another, while the sin [of a broken vow] should devolve upon his (i.e. my) head.
e) When the matter came before the Sages, they ruled: every gift which is not [so given] that if he [the recipient] dedicates it, it is dedicated, is no gift [at all].
Section one: This halakhah was basically taught above in mishnah 4:8. It is brought here as an introduction to the story.
Section two: The father could not enter his sons courtyard or eat of his food, because he was forbidden by oath to benefit from his son. It is unclear how this situation arose, whether the father or the son initiated the vow. In any case, there was clearly strife in their past. Now that his own son is marrying, the son wants his father to be able to attend the wedding and join in the feast. To solve the problem he gives the courtyard and the food to a third party. However, the third party declares that it is all dedicated to the Temple, which would make it impossible to use for a feast. The Sages rule that since the son does not want the dedication to be valid, he did not really give it to the third party. Therefore it is still his, and his father may not come to the wedding.
This is truly a sad situation, and it is clearly meant to demonstrate what disastrous results may arise from rashly-made vows taken against loved ones. Indeed, it may still ring as a warning in our ears, not to let our disagreements with family members cross the line of no return. It is a message that unfortunately too many families need.