This week's section is called Matot (Tribes). The opening topic is the laws of Nedarim, vows. It's a common misconception that Jews don't swear or make vows, which is actually a misunderstanding. There are two complex Talmudic treatises, Shvuot and Nedarim, that deal with the laws of oaths and vows, respectively. These concepts do exist in Judaism (because they are in the Torah), but ideally, one should avoid swearing or making vows given the grave and serious nature of such a commitment. In short, it's about the importance of not taking God's name in vain, one of the Ten Commandments.
For this reason, it is customary that when someone commits to a certain action, they say bli neder, which means "without promise," that is, although the person has every intention of carrying out what they said they were going to do, the gravity of a promise is not attached to that action.
Now, each mitzvah has a practical and simple aspect and a broader teaching on serving God. "Broader" means that it is not limited to the mitzvah itself, but teaches behaviors and values applicable to all other aspects of daily life.
Regarding promises, the Torah states at the beginning of this parashah (Numbers 30:3): "When a man makes a promise […] he shall not profane his word, as he does everything that proceeds from his mouth." The simple meaning of this verse is that the person making the promise must fulfill what they said. But what does it mean to "profane the word"? Rashi comments on this expression and explains that it means "he shall not make his words worldly," meaning, from a superficial reading, that when a person promises something and does not fulfill it, their words have been profaned, made worldly and ordinary; that is, they have stripped what they said of its credibility and virtue.
When we examine Rashi's words more closely, we will find a deeper and more comprehensive teaching. In Hebrew, the word for "words" (devarav) also means "business." So, Rashi is telling us, "He will not conduct his worldly business." And this is the most comprehensive teaching: everyone has "business," from work to the most basic needs like eating and drinking. At no point does the Torah require a person to abandon "business" to dedicate themselves to something else, however spiritual it may be. Rather, the Torah requires a person to "not conduct his worldly business," that is, to imbue the very actions they already perform with a deeper meaning, an energy that connects those actions to the service of God.
Herein lies one of the foundations of Judaism: the person must separate himself from the world, from daily life, but "he will not conduct his affairs in a worldly manner" but must imbue them with holiness and divinity.