Vows are very serious words that are spoken. Words mean things. Words have consequences. “G‑d instructed Moses regarding the laws governing how a person can make vows and oaths to G‑d.
[G‑d instructed Moses to tell the Jewish people,] “If someone makes a vow to G‑d . . . he must not violate his word.” Numbers 30:3
The word for “violate” in Hebrew (yacheil) comes from the word for “profane” or “unholy” (chol). The inner meaning of this verse is therefore that we should not make our words “unholy”; even our mundane conversation should be imbued with holy intentions and be consistent with the greater purpose of Creation, making a home for G‑d in this world.1 Likutei Sichot, vol. 13, p. 108.