Our Gemara on Amud Aleph refers to the halachic principle of mushba v’omed mehar Sinai. This means that certain oaths cannot be valid when made in regard to commandments, since one is already under oath that he took at Mount Sinai, and this new oath is meaningless on top of a preexisting oath, and therefore is not valid.

What is this oath that was made at Mount Sinai? We might assume that it is referring to the covenant that the Jewish people made at Mount Sinai. While not literally an oath, and certainly not one actually made by each inhabitant of every century, it is somehow considered binding on the entire people and its descendants. The Akeidas Yitschok (99) has difficulty with this idea. After all, there is no such thing as a parent passing an oath onto his children. What is this mechanism of obligation? And what makes this so-called oath binding? Akeidas Yitschok offers a parable:

Imagine a talented young man with an independent spirit and physical prowess who drew the ire of others because of his power but also drew the attention of the king. The king realized that this young person’s energies could be directed to his service and so he offers the young man an opportunity to settle on his royal estate. The king will offer legitimacy and protection in exchange for the lad’s fealty and service tending the royal estate. This happy arrangement worked for many years and even generations until one generation forgot the history of this arrangement and resented their servitude. They decided to leave the estate and find their own way in the world. They soon discovered that without the sanction and protection of the king, they were victims of persecution and assault from others who were jealous of their status. This led them to return and reaffirm their pact with the king.

This parable is Jewish history. When the Jewish people become restless, they question the covenant and want to operate without it. Yet, the rigors of oppression remind the Jews that, essentially, they must return to the estate and reaffirm their pact. Akeidas Yitschok explains that this is what it means when the Gemara states that the Jewish people reaffirmed the Mount Sinai covenant at the time of the Megillas Esther miracle (Shabbos 88a). The Jews reaffirmed their covenant as they realized, essentially, there was no choice. The Jewish people must stay connected to God because without His protection, there always seems to be some enemy lying in wait, ready to pounce upon any vulnerabilities.

Akeidas Yitschok sees this as a metaphorical obligation, as if it was an oath, not a literal oath per se, but a deep acceptance of the inevitability and the necessity of following the Torah, which is within the consciousness of the Jewish person. Therefore, no additional oath can be binding, as this preexisting recognition is as strong as an oath, so nothing can be added upon it.

I will add that this idea can help us understand the following tradition from Niddah (30b):

And a fetus does not leave the womb until the angels administer an oath to it… And what is the oath that the angels administer to the fetus? Be righteous and do not be wicked. And even if the entire world says to you: You are righteous, consider yourself wicked. And know that the Holy One, Blessed be He, is pure, and His ministers are pure, and the soul that He gave you is pure. If you preserve it in a state of purity, all is well, but if you do not keep it pure, I, the angel, shall take it from you.

How can a fetus make an oath? And even if it could, why would it be binding? However, if we understand the oath in a similar way to that of the Akeidas Yitschok, it is really about the inevitability of the consequences and responsibilities of life. The compelling need to keep this “oath” is not perforce an actual promise, but a part of the natural order, and failure to respect or acknowledge this will be at the person’s own peril.