Yiftach's oath or neder was, If You will indeed deliver the children of Amon into my hand, then it shall be, that whatsoever comes forth of the doors of my house to meet me, when I return in peace from the people of Amon, it shall be to Hash-m, and I will offer it up for a burnt-offering.'
and of course it turned out to be his daughter.
now of course here fulfilling the oath/neder would be(several) issur diorisas (offering something pasul; murder).
it seems obvious that a neder/shavua to do something assur min hatorah is void anyway. See e.g. shulchan aruch yoreah deah 215:5
alternatively-maybe the halacha is like when someone vows a pasul korban-they should get the value of the daughter and he must offer that? (i can't find the cite for this halacha at the moment about promising non kosher korbanot)
But why would he need to anul the neder through pinchas if its either void or that he should value the daughter and buy a kosher sacrifice?
George Weiss, silver spring, Maryland
Shalom George,
Thank you for a thoughtful set of questions. In short, the Halachah does not allow a Neder or Shevu'ah to commit a Torah transgression to take effect, so Yiftach was not permitted to fulfill his words through killing. This point is clear in the Rambam, Hilchos Nedarim 3:8-9, and in Shulchan Aruch, Yoreh Deah 215:5. Chazal also fault the leadership failure to arrange Hataras Nedarim. The Midrash says Pinchas did not go to Yiftach and Yiftach did not go to Pinchas, each guarding his own honor, and "between them the young girl was lost," and both were punished. See Bereishis Rabah 60:3.
You suggested redeeming the vow through value. That is exactly one Midrashic approach. Bereishis Rabah 60:3 records the view of Rebbi Yochanan, that Yiftach would at least be liable for Hekdesh Damim, while Reish Lakish says not even that. The same passage brings the familiar Halachah about consecrating an unfit offering: if a person says on a non-kosher or blemished animal, "Harei Zeh l''Olah," it is sold and he brings an Olah with the proceeds. According to this approach, there was a Halachically valid option that did not involve any Aveirah, and it highlights how tragic the failure to seek a proper ruling was.
You also asked why he needed annulment if the vow was void. The Ramban (Vayikra 27:29) explains that Yiftach erred by treating his words like a king's Cherem, as if leadership could bind a person. Even so, murder was never permitted, and the correct route was Hatarah or monetary redirection, not carrying out an Isur. That is why Chazal place the blame on the failure to consult Pinchas and on the ego that blocked annulment, not on any supposed "binding" force of a sinful Neder, as the Tanchuma in Parshas Bechukosai says, Yiftach lost his daughter because he was not a Ben Torah. According to this, it seems you are correct in your question, and the Gemara and Midrash regarding Yiftach and Pinchas is all according to Yiftach's mistake, l'Shitaso.
Finally, what actually happened to the daughter is a well-known dispute in the Rishonim. The Gemara in Ta'anis 4a and the Ramban read the text simply and condemn an actual sacrifice. The Radak to Shoftim 11, along with the Malbim and others, read the "Vav" in "veha'Alitihu Olah" as disjunctive, that if an animal came out it would be offered, but if a person came out the outcome would be "Yiheyeh la'Hashem," a consecrated life of celibacy. This fits the verse's description, "v'Hi Lo Yad'ah Ish." Even on the Ramban's side of the dispute, he still holds that the Halachah did not allow killing and that Yiftach should have used Hatarah or Hekdesh Damim. On the Radak's side, the language of the Neder never aimed at human sacrifice at all.
Kol Tuv,
Aharon Steiner