The Torah commands in Parashat Matot (Bamidbar 30:3) that if a person takes a vow, obligating himself in regard to some matter, “Lo Yahel Debaro” – he may not violate his word. The Gemara interprets this phrase to mean, “Lo Ya’aseh Debarav Hulin” – one may not make his words “profane” by failing to fulfill his promise. This refers to any sort of pledge which one makes – such as pledging to offer an animal as a sacrifice, or to donate money to the Temple treasury or another charitable cause, such as to a synagogue. If a person makes a pledge of this nature, and he fails to fulfill his promise, then he is in violation of this command. If, however, a person tells his fellow that he will give him something, and he fails to do so, then he does not transgress this particular prohibition. Of course, as the Sefer Ha’hinuch writes, it is a deplorable practice to commit to do something and then fail to follow through, and this transgresses the command of “Mi’debar Sheker Tirhak” – “You shall distance yourself from falsehood” (Shemot 23:7). But the command of “Lo Tahel Debaro” refers specifically to pledges involving a Misva, such as sacrifices or charitable donations. The Sages understood this command as implying that although a person himself may not violate his word, others may violate it. This refers to the concept of “Hatarat Nedarim” – the annulment of vows by either three laymen or a scholar with expertise in the area of Nedarim (vows). A person can seek the annulment of his vow, whereby the people in a sense make his word “profane” by revoking his pledge. A person who declared something Hekdesh (consecrated to the Temple treasury) can seek the annulment of his consecration, and it is then voided, and the item is divested of its consecrated status. As long as the consecrated item had not yet been given to the Bet Ha’mikdash, the pledge may be revoked through Hatara (annulment). Similarly, one who designated a portion of his produce as Teruma, or a portion of his dough as Halla, can have his designation annulled, as long as the consecrated portion had yet to be given to a Kohen. This Misva applies in all times and places, and to both men and women. One who fails to fulfill a Neder (vow) has violated this command, but he is not liable to Malkut, because failing to fulfill a pledge does not involve an action, and one is liable to Malkut only when transgressing by committing a forbidden act. If, however, a person violates a Shebua – an oath taken invoking G-d’s Name, then he is liable to Malkut even if he violates his oath without committing an action. Violating a Shebua is one of three exceptional transgressions for which one receives Malkut despite not performing an action. The other exceptions are cursing one’s fellow with Hashem’s Name, and Temura – declaring the transfer of sanctity from a consecrated animal to a different animal.