In the course of history the Jewish People has experienced many ascents and descents, often counteracting one another.
Opposite the conquest of the Land, there is the catastrophe of exile from it; opposite the building of the Temple, there is its destruction; and opposite the exile and the suffering, there are periods of return to the Land and its rebuilding.
In other words, even the most momentous events are, by their very nature, reversible.
There is no situation or state of being that does not have its antithesis, an event that is likely to cancel its effect and change its value.
The Giving of the Torah, however, is different.
It is an event from which there is no turning back. The change in essence and status brought about by the Giving of the Torah is such that the Jewish People cannot back out of it even if they so desire.
Ever since the Jewish People’s transformation at the revelation at Sinai into “a kingdom of priests and a holy nation,” it can no longer become something else.
To be sure, it is possible that individuals among the Jewish people, large parts of the people, or even the entire nation will at times not want to fulfill the Sinaitic commitment.
This non-fulfillment, however, does not negate the unique nature of the Jewish People.
It is merely an attempt not to live up to it, not to persist in it.
It is possible that the Sinaitic covenant will not be upheld at one time or another, but it cannot be abrogated or changed.
–Rabbi Adin Steinsaltz