In Parashat Matot, we read about the nullification of vows. In the Mishnah's tractates of Nedarim and Shevuot, as well as the Talmud, we further read several interpretations of different types of promises: a vow (נֶדֶר, neder), and an oath (שְׁבֻעָה, shevuah) for example.
The Man Of Emet
Specifically, in the Baraita, we learn that a Sage could annul a vow retroactively. This is because a person at such an elevated level speaks only "emet" (truth). Thus, what he says becomes true. Take Eliyahu HaNavi for example:
We later read that it did not rain in Erets Yisrael for three and a half years on account of Eliyahu's word. Furthermore, we see in the very same chapter the following statement from a widow he later helps:
What Is Greater: The Jew Or The Mitsvah?
The Halachic position whether or not a person's vow is binding offers several scenarios. I will explain two of these:
1. If a person says, "I am forbidden from observing Shabbat", it is an invalid oath. The reason being an oath cannot cancel another oath, since we, Yisrael, swore an oath to observe Shabbat (along with the entire Torah) at Mount Sinai.
2. However, if a person says, "Shabbat is forbidden to me", it remains a valid vow. In this instance, only a "Beit Din" (rabbinical court) can annul the said vow. Needless to say, such a vow would in theory only harm a person's well-being regardless.
So, what's the difference between the two?
The reason for this difference is because in the first instance the person forbids "themself", whereas, in the second instance, they forbid the "action" itself. Allow me to elaborate.
A person can be a "rasha" (wicked person) today, and a "tsadik" (righteous person) tomorrow. Who we are changes with every passing moment (hopefully for the better). Thus forbidding oneself, is logically more lenient.
In contrast, forbidding an action is correctly binding as the action itself cannot change as it is independent of the person. Thus, in the second instance, this requires more stringency to annul.
The Beginning, Middle, And End
In Hebrew, the word "emet" (truth) is spelt "אֶמֶת". The three letters are the first (א), middle (מ), and last letter (ת) of the Hebrew Alef-Bet, respectively. As HaShem created the universe through Ten Utterances, "emet" (truth) is thus the beginning, middle, and end of all existence.