Not Saying Hashem’s Name in Vain

The Gemara in Nedarim (7b) says, “Rav Chanin said in the name of Rav: Whoever hears the utterance of the Divine name [in vain] from his friend has to excommunicate him. If he doesn’t, he himself should be excommunicated.” The Ran there references the Gemara in Temurah (3b) that says that someone who says Hashem’s name in vain has violated the pasuk, “Hashem your G-d, you shall fear” (Devarim 6:13). The Gemara says further that saying Hashem’s name in vain causes a person to become poor. In fact, the very first Mishnah in Nedarim also is a lesson in the severity of saying Hashem’s name in vain, according to Reish Lakish.
The Mishnah says that kinuyei nedarim are valid formulations of a vow. According to Reish Lakish (Nedarim 10b), to prevent the possibility of people’s saying Hashem’s name in vain, the Sages invented new words to be used in the formulation of a vow. Originally, one could have said, “This loaf of bread should be forbidden to me like a korban [sacrifice].” However, that would lead to a possibility of people saying “korban l’Hashem” since that is the text of a pasuk in the Torah. Then people may delete the word korban altogether and only use Hashem’s name, thereby uttering Hashem’s name in vain. To preclude that possibility, the Sages encouraged the use of other words that are not associated with Hashem’s name. These words are called kinuyei nedarim.