The gemara (Shabbat 88a) learns from the pasuk, "They stood at the bottom of the mountain" (Shemot 19:17) that He held the mountain over them like a tub, threatening them that if they did not accept the Torah, "There would be your grave." So it turns out that after Bnei Yisrael willingly accepted upon themselves, before the Torah was given, to keep all the words of the Torah, they still needed to be threatened. Many commentaries wonder about the need for this, and several answers have been given.

The following explanation may be close to the truth. Man has the power to desire something strongly, and man has the power to carry it out. On a theoretical basis, the two are directly connected to each other. When a person wants something, he will carry through on it. However, in practice there is a big difference between desire and actualization. There are many things that we know are good and worthwhile and yet they remain within the realm of plans that one would like to do … but does not do them. This is because carrying out things requires effort, giving up on conveniences, and overcoming obstacles. To overcome these, good will is insufficient.

We remember well the days of struggle against the British Mandate before the establishment of the State. The struggle was very, very difficult and included a lot of "inconvenience." Yet, the Jewish inhabitants of Eretz Yisrael stood up to the challenge nobly. They were willing to pay the price, whatever was necessary to reach the goal. In contrast, from the time of the establishment of the State, we have often seen a relaxation of the tension, a weakening of resolve, and a lack of carrying out of that which needs to be done. It is not that there is no possible way to succeed but is due to a lack of stubbornness to get the job done at any price. What caused the difference? It is because at the time of the establishment of the State, the question was raised in the sharpest manner, as people felt that there was no alternative. It was clearly a make or break situation. As people used to say: "We have a secret weapon, whose name is aleph bet: ein bereira (there is no choice)." As they would say in the Navardok Yeshiva: "When there is a possibility to pass, it is necessary to pass; and when it is necessary, then it is possible."

The same attitude is true regarding the acceptance of the Torah. Certainly, Bnei Yisrael’s unanimous response of na’aseh v’nishma (we will do and hear) was sincere and expressed the people’s good will. However, Hashem knew the characteristic of the people and that not much later they would dance around the Golden Calf. After all, there is a great distance between the theoretical and the practical. It is easy and pleasant to dance around the calf, and it is difficult to "kill oneself in the tent of Torah." Therefore, there is a need for Divine Assistance, help which comes to one who is sincere in his desire to follow the straight path. This is what Chazal described as holding the mountain over their head. In other words, Hashem was telling them that not just good will would get them to accept the Torah, but that actually there is no choice. Israel’s existence depends on the extent to which they accept the Torah. The feeling of ein bereira gives the good will the ability to carry out their desire in practice.