Does Bal Te'acher apply also to Nedavah?
Rosh Hashanah, 5b: We learn via a Gezeirah Shavah "Neder" "Neder" from Pasuk 24, that, just as there, the Pasuk incorporates Nedavah, so too, here.
Why does the Torah insert the words "la'Hashem Elokecha"?
Rosh Hashanah, 5b: To incorporate Damim, Arachin, Charamos and Hekdeishos in the prohibition. 1
Yerushalmi Rosh Hashanah, 1:1: To incorporate Hekdesh Bedek ha'Bayis in the prohibition. 2
Why is the La'av of Bal Te'acher written after that of Ribis?
As opposed to Ribis, for which one is not permitted to fulfill an agreement to give it to a Yisrael 1 one who declares a Neder must keep his word at all costs, and even do so without delay.
What is the Shi'ur of 'Bal Te'acher'?
Rashi and Targum Yonasan: Three Yamim-Tovim (Pesach, Shavu'os and Sukos, in whichever order they occur following the Neder - Rosh Hashanah, 4a, according to the Chachamim). 1
Rosh Hashanah 4a (according to R. Shimon): It is three Yamim-Tovim, starting from Pesach.
See Sifsei Chachamim.
What are the implications of "Ki Darosh Yidreshenu mi'Imach"?
Seforno: It implies that if you don't pay what you promised on time, Hashem will claim it from you against your will.
Oznayim la'Torah: The Torah writes the double Lashon "Darosh Yidr'shenu Hashem Elokecha me'Imach" - like we find by Ya'akov Avinu, whom Hashem reminded twice to go and fulfil his Neder. 1
Oznayim la'Torah: See In Bereishis 31; 13 and Bereishis 35:1.
What are the implications of the phrase "Vehayah b'cha Chet"?
Seforno: It implies that even if you keep your promise in this way (by force), you will still be punished for delaying it.
What are the implications of the word "Vehayah b'cha Chet"?
Targum Yonasan Rosh Hashanah, 5b): "b'cha Chet", 've'Lo be'Korbancha Chet' - The Korban does not become Pasul even after three Yamim-Tovim have passed, because 'the moment one designates it, it enters the storehouse of Hakadosh-Baruch-Hu'. 1
Rosh Hashanah, 6a: "b'cha Chet", 've'Lo be'Isht'cha Chet' - The sin of Bal Te'acher will not cause the death of one's wife. 2
See Peirush Yonasan.
This is like Tosfos (6a DH 'Ela'; according to Rashi, the Gemara is not discussing Nedarim). The Gemara says that she is prone to die before he fulfills his Neder, but not after he has fulfilled it, even if he delayed (See also Torah Temimah, note 121). However, the Midrash Bereishis 35:1 explicitly states that Rachel died (after Ya'akov fulfilled his Neder) due to his delay! (PF).
