As our sages tell us, the connection between the Festival of Shavuot and King David is rooted in the fact that David died on Atzeret (and was also born on Atzeret - Shavuot, as HaShem completes the days and years of Tzaddikim). In the Talmud Yerushalmi (Beitza ch.2 halacha 4; Hagigah ch.2 halacha 4): "Rabbi Yossi (the son of) Rabbi Bon said: David HaMelech died on Atzeret and all of Israel were (in the state of being) onenim (onen = the first stage in mourning, when one's deceased lies before him, before the burial) and they offered their sacrifice the following day." The Yerushalmi emphasizes that since David died on the Yom Tov of Shavuot, all of Israel were onenim, because all of Israel become onenim when the king dies (Pesachim 70b). Therefore, they could not offer the Hagigah sacrifice, and they offered it the next day.
 

The Talmud Bavli (Shabbat 30a) describes the death of David HaMelech, and states that he passed away on Shabbat. If we say that the two Talmudim do not contradict each other, on that year Shavuot fell on Shabbat, as is brought down in Ruth Rabbah (ch. 3): "He died on Atzeret which fell on Shabbat (which was possible only in their time, when months were determined according to the sighting the moon)." And this raises a great question, which we will explain.
 

The Mishnah in Hagigah (17a) presents a disagreement between Beit Hillel and Beit Shammai on the issue of sacrificing Olot (burnt - offerings) and Shelamim (peace -offerings) on Yom Tov. According to Beit Shammai, Shelamim are offered on Yom Tov because part of the sacrifice is eaten by Hediot (Israelites who bring the sacrifice) and therefore are considered Ochel Nefesh (food for consumption on Yom Tov), however, Olat Rayah (the burnt-offerings brought by individuals on the festival) are not for consumption, and therefore the sacrificing is postponed to the next day. In contrast, Beit Hillel reason that both Shelamim and Olot, which are for the purpose of that day, are sacrificed on Yom Tov.
 

Therefore, according to Beit Shammai, Isru Chag, the day after Shavuot, is called "Yom Tevoach" (the day of slaughtering the Olat Rayah sacrifices of the festival). On this day (when Isru Chag is a weekday, not Shabbat) all the Olat Rayah sacrifices of the festival are slaughtered. According to Beit Hillel, there is no need for a Yom Tevoach, as the Olat Rayah is sacrificed on Yom Tov itself.
 

However, when Atzeret falls on Shabbat, in this case Beit Hillel agree with Beit Shammai that the Olat Rayah is not sacrificed on Shabbat because of the severity of the Shabbat, and in this instance Beit Hillel concur that there is a Yom Tevoach on Sunday, Isru Chag of Shavuot.

The Gemara learns there that there are seven days of tashlumin (offering sacrifices pertaining to the festival) through a hekesh (similarity) to the Festival of Matzot.

In Yerushalmi mentioned at the beginning, it is learned that there are tashlumin for Atzeret from the fact that David died on Atzeret and all of Israel were onenim (and couldn't offer sacrifices) and therefore they had to make up the Olat Rayah the following day. But if, as the Bavli states, Atzeret fell on Shabbat that year, then why did the Yerushalmi give the fact that they were onenim as the reason for tashlumin? It could have said that when Yom Tov falls on Shabbat, according to all opinions they couldn't offer Olat Rayah!
 

According to the Tosefot in Hagigah, we are forced to say, allegorically, that "the bread fell into the pit" (meaning that our line of reasoning came to an impasse) since the Talmudim disagree: According to the Bavli, David died on Shabbat, but not necessarily on Atzeret (and consequently there is no indication that he was born on Atzeret). And according to the Yerushalmi, he died on Atzeret but certainly not on Shabbat.
 

There have been several attempts by the Acharonim to reconcile between the Talmudim. I want to present the brilliant solution of the Chatam Sofer to this riddle.

The Chatam Sofer explains the Bavli (Shabbat 30b): When HaShem told David: "On Shabbat you will die" that David was not certain whether this meant Shabbat Bereshis (the Shabbat of every week), or Yom Tov, which as we know, is also called Shabbat. Therefore, he occupied himself with Torah all of every Shabbat and also all of every Yom Tov because of this uncertainty. And what is written in the Gemara, that "every Shabbat he sat and read (learned) all the day" refers to all the Holidays and Shabbatot of the year. And the Chatam Sofer concludes: "And in the end he died on Atzeret which fell on a weekday." And this way the Bavli does not contradict the Yerushalmi, since the Shabbat mentioned there is not specifically (what we call) Shabbat.

I wish to mention more of the sweet Torah of the Chatam Sofer on a closely related subject, that of King David's death and the dilemma of his son Shlomo regarding carrying the dead.
 

The Gemara says there: "Shlomo sent to the Beit Midrash: Father died and is lying in the sun, and the dogs of my father's house are hungry. What shall I do? They answered: cut up a carcass and put it before the dogs, and your father – place a loaf or a child on him and carry him." The Acharonim asked: way was it necessary to place a loaf or a child on him – David was wearing regal clothes, and he could have been carried along with his clothes. And should you say that his clothes were muktza because it is prohibited to use the clothing of a king, his son Shlomo was permitted to wear them! Additionally the Chatam Sofer asks: why did Shlomo ask about the dogs being hungry? Didn't this ever happen before? What did they do for the dogs of the king's house on Shabbatot and holidays in the past?! There is nothing new under the sun, and that which was is that which will be.

The Chatam Sofer answers both questions with one brilliant stroke: In David's day, it never happened that the dogs were hungry on Shabbat! They kept quiet until Motzei Shabbat because David was a Chassid and HaShem never brought him into a situation where it was necessary to permit muktza or nolad for the benefit of animals and to cut up a carcass on Shabbat. And when Shlomo heard that immediately after his father's death the dogs howled for prey, he thought: this never happened before, so what is different today from yesterday? And he immediately realized that he hadn't reached his father's level and was not worthy of wearing his clothing.

Now we can understand Shlomo's question to the sages: "Father died and is lying in the sun. And if you will tell me: carry him along with his regal clothes, this is impossible, because the dogs of my father's house are hungry, and this this is a sign that his clothes are muktza for me, as I am not worthy of wearing them. Therefore, what shall I do?" Consequently, they answered him: put a loaf or a child on him and carry him.

Of this it is said (Mishlei 24:26):"Lips should kiss the one who gives a good answer."

May the words of the Torah always be sweet and delectable to our mouths, and may we and our offspring all know Your name and learn Your Torah lishma.