Parshas מטות begins with the דינים of נדרים. The פסוק states
איש כי ידור נדר לה’….לא יחל דברו ככל היוצא מפיו יעשה
When making a נדר, one is obligated to keep his word. Rashi notes that לא יחל דברו means he should not make his words חולין, mundane, rather he should keep them holy, as he promised when making the נדר.
How do we understand this concept, that merely by uttering words, we’re able to create a new reality of קדושה that is Halachicly binding?
The נתיבות שלום explains that the mouth of a Yid is a holy vessel, that was created for the purpose of speaking דברי קדושה, such a תפילה and תורה. That designation makes one’s mouth similiar to כלי שרת, the vessels that were utilized in the בית המקדש to conduct the עבודה. The הלכה is that anything that is contained in a כלי שרת becomes automatically הקדש, as it is absorbed within a vessel that is קדוש. Similarly, since our mouth was created for דברי קדושה, it too becomes like a כלי שרת, sanctifying the words it utters. And that is how by merely speaking the words of a נדר, a new איסור or קבלה was created.
We can now understand the words of לא יחל דברו, he should not make his words חולין. The תורה is highlighting the unique power of קדושה we can create through properly utilizing our mouth. We can sanctify that which we say, by properly utilizing the power of speech for דברים שבקדושה, and by avoiding לשון הרע and ניבול פה. And then, our mouths become כלי שרת, vessels of קדושה, elevating us and our surroundings.
We’ll conclude with a story that highlights this point. Harav Yaakov Kaminetzky was a classic Litvak, a product of the Slabodka Yeshiva. Yet, his entire life, he was מקפיד on not eating Gebrochs on Pesach, a well-known, Chasidish מנהג. The story of how he adopted this מנהג dates back to his days in Yeshiva. One year, shortly before פסח, Rav Yaakov was invited by a resident of Slabodka to join his family for the סדרים. Not being sure of the Kashrus standards in the man’s home, yet not wanting to offend him either, Rav Yaakov came up with the perfect excuse, ” My מנהג is to not eat Gebrochs.” The man understood, and Rav Yaakov ended up having the סדרים elsewhere. But from then, and for the rest of his long life, a period of over 70 years, Rav Yaakov never again ate Gebrochs on פסח.
Indeed, our mouth and our words, are holy and powerful.