Parshat Mattot begins with the verses (Bamidbar 30:2-3), “And Moshe spoke to the heads of the tribes of the children of Yisra᾽el, saying, “This is the matter which the Lord has commanded. If a man vows a vow to the Lord, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceeds out of his mouth.”
The Torah continues with several pesukim that detail and highlight various aspects and qualifications of the laws of nedarim, or vows.
As the commentaries point out, this is one of the rare - perhaps the only - times in the Torah where Moshe is listed as conveying the word of Hashem to the people, without the Torah detailing the initial communication from Hashem to Moshe. Additionally, the Torah’s use of the phrase, “This is the matter which the Lord [Hashem] has commanded,” is not found in reference to any other prophecy conveyed by any other prophet.
Rashi (ad. Loc.) explains: “...the [other] prophets prophesied with “So says Hashem”; Moshe surpassed them, as he prophesied with the phrase “This is the word of Hashem.” Thus, the evidence indicates that the Torah is communicating a subtle but poignant message within the parameters of the halakhic concept of vows and promises.
Rav Shimon Schwab, may his memory be a blessing, writes (Me’ein Bais Ha’Shoeivah ad. loc.) that in reality, the Torah is the word of Hashem, and the 613 mitzvot, which, while serving as the spiritual pathway to the infinite, should represent the finite expression of those pathways in our physical realm. However, the Torah offers the possibility of adding to those mitzvot through the concept of nedarim, whereby actual Biblical prohibitions will result, and one who prohibits an item on themself using this halakhic concept will find that the prohibition that is put in place is on the same level as eating pork, for example. (See the Sefer Ne’eot Ha’Deshe (ad. loc.), written by the Rebbe of Sochatchov, who wonders why adding a prohibition in this capacity does not violate the rule of “Do Not add” to the words of the Torah.)
Thus, we can explain, that the abilities of the spoken word emphasized within the guidelines of the laws of vows highlights the great power and responsibility invested within each and every one of us when using the faculty of speech. Echoing this theme, the Torah details the laws of vows as being given by Moshe Rabbeinu, without mentioning the initial delivery of these concepts from Hashem to Moshe - thereby demonstrating that one can craft and create prohibitions of the Biblical scale using speech, at their own initiative.
Dedicated in memory of all those who have perished and sacrificed for Am Yisrael.