The Torah refers to Shavuos as “Yom HaBikkurim – the Day of the First Fruit Offerings,” making no mention of it as the Festival of Kabbalas HaTorah. Nonetheless, this is how it is widely observed and how it is called in our prayers: “zman matan toraseinu – the time of the giving of our Torah.” It is therefore all the more fascinating that a calculation of the dates provided in the Chumash and Gemara reveal that the Torah was not given on the 6th of Sivan at all, but on the 7th, as the Magen Avraham and Maharsha point out.
The Torah tells us that Hashem commanded Moshe to prepare Bnei Yisrael for Kabbalas HaTorah for two days, after which He would grant the Torah on the third:
ויאמר ה' אל משה "לך אל העם וקדשתם היום ומחר וכבסו שמלותם. והיו נכונים ליום השלישי כי ביום השלישי ירד ה' לעיני כל העם על הר סיני."
Hashem said to Moshe, “Go to the nation and sanctify them today and tomorrow. Have them wash their clothes and be prepared on the third day, for on the third day Hashem will descend on Har Sinai before the eyes of the entire nation.”
However, Moshe did not precisely follow this instruction, but added a third day of preparation of his own volition, as the verse states:
ויאמר אל העם "היו נכונים לשלשת."
He said to the nation, “Prepare yourselves for three days.”
Based on these and other sources, the Gemara concludes that Bnei Yisrael arrived in the Sinai Desert on Rosh Chodesh Sivan and rested that day from their exhausting journey. On the 2nd of Sivan, Hashem informed Bnei Yisrael, “You shall be for Me an empire of noblemen and a holy nation.” On the 3rd they were commanded to prepare themselves for Kabbalas HaTorah. Then followed the three days of preparation (two of which were commanded by Hashem Himself, while the third was added by Moshe). Thus, only on the 7th of Sivan did they actually receive the Torah.
Furthermore, the Gemara states that Bnei Yisrael left Egypt on a Thursday and received the Torah on Shabbos. If so, the Torah was surely given on the fifty-first day after Pesach, not the fiftieth day as it is commonly observed. Some see this as a hint from the Torah that we were destined to observe the 7th of Sivan as the second day of Yom Tov in exile, but this still does not help us understand how we can call the 6th of Sivan: “zman matan toraseinu.” When was the Torah really given, on the 6th of Sivan or the 7th?
The Maharsha explains as follows:
והכוונה בזה לפי שלא היו ישראל אז ראוים לחכמת התורה עד שיטהרו ויקדשו עצמם מכל טומאת מצרים שיצאו משם כמ"ש כל שיראת חטאו קודמת לחכמתו וכו' וע"כ היתה הטהרה במספר שבעה שבועות ויום חמשים שהם מספרים קדושים כענין שבת שמיטים ויובלות ולפי שביום נ' נגמרה הטהרה שזכינו אחר כך ביום נ"א לקבל התורה קבע הש"י אותו יום חמשים לחג שבועות כי יראת חטא קודמת לחכמה במעלה ובזמן.
Bnei Yisrael could not be worthy of the wisdom of the Torah until they had first purified themselves of the negative influence they had received in Egypt. Our Sages warn us that fear of sin must always precede wisdom. [Thus, Bnei Yisrael had to reach a certain level of yiras Shomayim before they could grasp the Torah.] Their purification process entailed seven weeks of seven days each, followed by a fiftieth day [that consolidated their fifty individual steps towards purity]. This paralleled the seven year shemittah cycle, which is repeated seven times and then followed by yovel.
The fiftieth day was when Bnei Yisrael had reached the level of purity necessary to receive the Torah on the fifty-first. Therefore, the fiftieth was marked as the Festival of Kabbalas HaTorah, in deference to the purity and fear of sin that must precede wisdom, and is even more valuable than wisdom itself.
The Maharsha thus explains that Shavuos is celebrated on the 6th, not in memory of Kabbalas HaTorah itself, but in memory of the preparations that were necessary to obtain the yiras Shomayim that is a prerequisite to Torah. Still, this does not exactly answer the question of how we can say in davening on the 6th of Sivan, “zman matan toraseinu – the time of the giving of our Torah,” when the Torah was in fact not given until the next day.
The laws of conversion to Judaism are deduced by comparison to how our forefathers converted as a group into the Chosen Nation, as the Rambam explains:
א: בשלשה דברים נכנסו ישראל לברית במילה וטבילה וקרבן. ב: מילה היתה במצרים שנאמר "וכל ערל לא יאכל בו", מל אותם משה רבינו שכולם ביטלו ברית מילה במצרים חוץ משבט לוי ועל זה נאמר "ובריתך ינצורו." ג: וטבילה היתה במדבר קודם מתן תורה שנאמר "וקדשתם היום ומחר וכבסו שמלותם", וקרבן שנאמר "וישלח את נערי בני ישראל ויעלו עולות" על ידי כל ישראל הקריבום. ד: וכן לדורות כשירצה העכו"ם להכנס לברית ולהסתופף תחת כנפי השכינה ויקבל עליו עול תורה צריך מילה וטבילה והרצאת קרבן, ואם נקבה היא טבילה וקרבן שנאמר "ככם כגר", מה אתם במילה וטבילה והרצאת קרבן אף הגר לדורות במילה וטבילה והרצאת קרבן. ה: ... ובזמן הזה שאין שם קרבן צריך מילה וטבילה וכשיבנה בית המקדש יביא קרבן.
1: Bnei Yisrael entered into the Covenant by following three procedures: Bris Milah, immersion in a mikvah, and sacrificial offerings. 2: Their Bris Milah took place in Egypt, as the verse states [concerning the Korban Pesach offered there], “No uncircumcised person may eat from it.” Moshe had to circumcise them, since while they were in Egypt they had all abandoned the Bris Milah, except for the Tribe of Levi, of whom it is said, “They guarded Your covenant.” 3: Their immersion took place in the Desert before Kabbalas HaTorah, as it is written, “Sanctify yourselves today and tomorrow and wash your clothes.” A sacrifice was also offered then, as it is written, “He sent the youths of Bnei Yisrael to offer sacrifices.” These sacrifices were offered on behalf of the entire Jewish nation. 4: Throughout the generations, if a gentile wishes to enter the Covenant, to rest beneath the wings of the Shechinah and accept the yoke of Torah, he must be circumcised, immerse in a mikvah, and offer a korban, whereas a gentile woman need only immerse and offer a sacrifice. It is written, “As for you, so for the convert.” Just as you [entered the Covenant] by means of circumcision, immersion and sacrifice, so must converts throughout the generations be circumcised, immerse and offer a sacrifice. 5: … In times when sacrifices cannot be offered, the convert needs only circumcision and immersion. When the Beis HaMikdash will be rebuilt, he must then offer a sacrifice.
Additionally, a convert must commit to fulfilling all the mitzvos, just as our forefathers did when they proclaimed, “Na’aseh v’nishmah – We will do and we will listen.” The Poskim infer from the Gemara that there are two stages in this commitment. First, the convert must accept Hashem’s sovereignty in a general sense. Then, as he prepares to immerse in a mikvah and conclude his conversion process, he is briefly taught some basic mitzvos, to which he must reaffirm his commitment.
The commitment we made at Har Sinai to observe the Torah also involved two stages. On the 6th of Sivan we accepted Hashem’s sovereignty and made a general commitment to observe the entire Torah. At that point we had purified ourselves from false ideologies, negative character traits and selfish desire, to the extent that we were truly able to make this commitment. This was the essence of Kabbalas HaTorah, even though it was not until the next day that we received the details of the Torah.
With this we can understand the stanza from Dayeinu, “Had He brought us to Har Sinai but not given us the Torah, it would have been enough for us.” Even if we had not received the details of the Torah’s laws on the 7th of Sivan, we still would have been greatly benefited by the general commitment to Hashem’s service that occurred on the 6th of Sivan, which is eternally recognized as the true anniversary of Kabbalas HaTorah.
 Bamidbar 28:26
 Shulchan Aruch: Orach Chaim, introduction to 494
 Commentary on Aggadatah: Avodah Zarah 3a
 Shemos 20:10-11
 Shemos 20:15, Rashi
 Shemos 19: 6
 Shabbos 86b-87a
 Shabbos 86b
 Maharsha, Commentary on Aggadatah: Avodah Zarah 3a
 Magen Avraham, ibid
 Pirkei Avos 3:9
 Yevamos 46a; Krisos 9a
 Shemos 12:48
 Devarim 33:9
 Shemos 19:10
 Shemos 24:5
 Rambam, Hilchos Issurei Bi’ah 13: 1-5
 Yevamos 47b. See Teshuvos Chemdas Shlomo Y.D, 29-30