Hashem said to the nation (Shemos 19:11) והיו השלישי ליום נכונים, "Be prepared for the third day." Be prepared for matan Torah. Every year, on Shavuos, Hashem gives us the Torah again, and we should prepare ourselves for matan Torah.
The dates of Pesach and Yom Kippur are written explicitly in the Torah. Similarly, the dates of all yomim tovim are clearly stated in the Torah. The exception is Shavuos. About Shavuos, the Torah writes that it is on the fiftieth day of Sefiras Ha'Omer, but it doesn't state the date and month. Indeed, the date can vary. It depends on how many days Rosh Chodesh Iyar and Rosh Chodesh Sivan will be. Therefore, the Gemara says that Shavuos is on either the fifth, sixth, or seventh of Sivan. (In our times, Shavuos is always on the sixth of Sivan, because Iyar always has two days of Rosh Chodesh and Sivan one day. But when Rosh Chodesh was established through Kidush HaChodesh, with witnesses who saw the new moon, the date of Shavuos would differ.)
Shavuos is different than all yomim tovim to imply that when the Jewish nation finishes preparing for the yom tov, it is then that they will receive the Torah. Shavuos isn't dependent on a set day, but rather on the preparation of the Jewish nation.
The Kedushas Levi zt'l writes, "If a person merits, he will hear Hashem's voice on Shavuos when He says אלקיך 'ה אנכי. How could a person not prepare for this? Millions of malachim tremble before Hashem's magnificence. Certainly, us human beings... Three days of preparation isn't enough. Even if one prepares the entire year, it also isn't enough."
One Friday night on parashas Yisro, Rebbe Levi Yitzchak of Berdichev zt'l said at his tish, "Tomorrow, when the Aseres HaDibros are read, the people who have holy ears will hear Hashem say the Aseres HaDibros..."
He said that he was expecting to experience the same intensity on Shavuos, but it didn't happen on Shavuos.
It states (Shemos 19:3) ההר מן 'ה אליו ויקרא האלקים אל עלה ומשה, "Moshe went up to Hashem, and Hashem called to him from the mountain." The Or HaChaim notes that Moshe had to climb the mountain, and then Hashem called out to him. "Because holiness doesn't come to a person unless he prepares for it. As the Zohar states, 'An arousal from below causes an arousal Above.'" So, we must prepare for the yom tov and matan Torah, and then we will receive it.
In the Haggadah Shel Pesach, we say, דיינו התורה את לנו נתן ולא סיני הר לפני קרבנו אילו, "Had Hashem brought us to Har Sinai and not given us the Torah it would be enough." It seems that just being at Har Sinai had a benefit, even without matan Torah. What was the benefit?
The Chida (Leiv Dovid 31) zt'l explains that when they stood at Har Sinai, they prepared to receive the Torah, and due to their preparations, they perceived the divine secrets of the Torah (even before it was actually given). Therefore, we say that for arriving at Har Sinai דיינו.
A person got married, and a month later, he divorced. The following year, he married again, but a month later, he divorced again. This pattern repeated itself numerous. He got married, and after a month, there was a divorce. Understandingly, with each wedding he made, fewer people attended, and the joy was less. No one expected the marriage would last for longer than a month.
One year, this man was engaged for marriage and invited everyone to come. "This time the marriage will last!" he told everyone. "Everyone should come and rejoice at my chasunah!" "Why do you think this time will be different?" his friends asked him. He explained that this time he prepared for the chasunah; he went to a chasan teacher to learn how to get along in marriage, and therefore, it will be different this time.
The nimshal is that every Shavuos, there is a chasunah. Keviyachol, Klal Yisrael marries the Torah. But the marriage doesn't last. Soon after Shavuos, he stops learning Torah. His kabalos for the new year cease. However, if he prepares for Shavuos, there is a greater chance that the marriage will endure this time, and he will remain with Torah the entire year and for years to come.
The Avodas Yisrael of Kozhnitz zt'l added, "Even today, it is certainly possible to hear Hashem say the aseres HaDibros. This will occur if he cleans and purifies his ears, and then he can also hear it!" This means he should prepare himself for matan Torah.
The Satmar Rebbe zt'l said that ונשמע נעשה means if a person prepares himself with נעשה, deeds, he will merit נשמע, to hear Hashem say אלקיך 'ה אנכי.
The Chizkuni (introduction to Chumash) writes, "I swear by my soul that I, Chizkiyah, heard Hashem's voice in my dream, saying the Aseres HaDibros..."
The Divrei Yechezkel of Shinov zt'l said that on Shabbos parashas Yisro, when his father, the Divrei Chaim of Sanz zt'l, read the Aseres HaDibros, he felt as though he was standing at Har Sinai and was hearing the Aseres HaDibros from Hashem. He heard the shofar and the thunder, saw the lightning, and experienced everything else that took place at matan Torah.
It states (Shemos 19) ידבר משה, "Moshe will speak [the Aseres HaDibros]" - in the future tense. The Beis Aharon zt'l writes, "This is because Moshe Rabbeinu will speak in every generation to every Yid who purifies himself to receive the Torah..."
