David Melech Yisrael Chai Vekayam

Divrei Chaim mentions the difference between Yaakov Avinu lo meis on the one hand, and david melech yisrael chai vekayam on the other, though does not elaborate on the exact distinction between the two Rav Kook makes.

David Melech Yisrael Chai veKayam occurs specifically on Rosh haShana 25a:

א"ל רבי לר' חייא זיל לעין טב וקדשיה לירחא ושלח לי סימנא דוד מלך ישראל חי וקים

To use the point by point summary here:

(b) R. Chiya saw the old moon on the morning of the 29th of Elul;

1. He threw a clod of earth at it, as he wanted it to be invisible now so that the new one could appear at night (and the month could be abridged, thereby separating Yom Kipur from Shabbos).
2. Rebbi told him to go to Ein Tav and sanctify Rosh Chodesh there, and to send the message "David Melech Yisrael..."

See Insights to the Daf for elaboration, such as the following excerpt:

QUESTION: The Gemara relates that Rebbi told Rebbi Chiya that when he sanctifies the new month, he should send Rebbi a message saying, "David Melech Yisrael Chai v'Kayam." RASHI explains that the verse (Tehilim 89:37) compares the Davidic dynasty to the moon.

Why is Malchus Beis David compared to the moon?

(a) This analogy can be understood based on the words of the Midrash (Shemos Rabah 15; see also RABEINU BACHYE to Bereishis 38:30, cited by SHULCHAN ARUCH OC 426:2). The Midrash teaches that just as the moon waxes and wanes over a thirty-day period, so, too, the power of the kingdom of Yisrael "waxed and waned" over a period of thirty generations. For fifteen generations it grew until it was full -- from Avraham Avinu until Shlomo ha'Melech, and for the next fifteen generations it waned, coming to its end at the reign of Tzidkiyahu ha'Melech whose eyes were blinded by the enemy at the time of the destruction of the Beis ha'Mikdash (Yirmeyahu 52:11). The blinding of Tzidkiyahu, like the complete loss of the light of the moon, was a sign that the Davidic dynasty had ended. The return of the moon's light after the Molad is a sign that the dynasty of David ha'Melech will return to its former glory.

For this reason Rebbi established that Malchus Beis David be mentioned as a sign that the new month was declared. The MAHARATZ CHAYOS adds, based on the Yerushalmi in Sanhedrin, that it indeed was the common practice to announce the new month with the phrase "David Melech Yisrael..." The Chachamim viewed the new moon as a sign of hope and anticipation for the restoration of the autonomy of the Jewish people and the Davidic dynasty. This is also the source for the present-day custom to mention this phrase during Birkas ha'Levanah.

As such, it does not seem that the one intended as Chai veKayam is David haMelech in any literal sense. Rather, it is to the Davidic dynasty. If this is indeed so, it should not be mustered as any sort of proof such as, e.g., that a religiously can physically die yet be "alive" and so be mashiach. Of course, any one can reinterpret this and claim that it actually refers to David. But there is no need to do so, and we see how it is may be understood by one such as Rashi on a peshat level.

I further heard in shiur the idea that the authorities (Romans) were supressing this declaration of the new moon, such that all this had to be in secret code, and this was what "David melech yisrael" was. I would add that if this was indeed a code, and Rebbi, who was Rabbi Yehuda haNasi, descended from David, was circumventing this ban and exercising this power to declare the new month, then this type of message would be quite appropriate.

This is the actual Rashi as well as Rabbenu Chanenel, pictured to the right.

Thus, Rashi cites a pasuk in Tehillim to show that he (or his dynasty -- it does not really matter) is compared to the moon. Thus, in effect, this statement is code, where what is really being spoken of is the moon, not David. This does not in any way necessitate a belief that King David did not die, against what it says in Melachim Aleph, perek 2:

י וַיִּשְׁכַּב דָּוִד, עִם-אֲבֹתָיו; וַיִּקָּבֵר, בְּעִיר דָּוִד. {פ}

10 And David slept with his fathers, and was buried in the city of David. {P}

Burial would be quite unconfortable for a living person.

The pasuk Rashi cites is from Tehillim 98:

לו אַחַת, נִשְׁבַּעְתִּי בְקָדְשִׁי: אִם-לְדָוִד אֲכַזֵּב.
לז זַרְעוֹ, לְעוֹלָם יִהְיֶה; וְכִסְאוֹ כַשֶּׁמֶשׁ נֶגְדִּי.
לח כְּיָרֵחַ, יִכּוֹן עוֹלָם; וְעֵד בַּשַּׁחַק, נֶאֱמָן סֶלָה.

Where we should note how pasuk 37 talks about zar'o, such that it refers to the dynasty rather than the man.

Rabbenu Chananel also says that the malchut of bet david is established forever, citing the same pasuk. And he explains that it is a siman, that the sighting of the lavana is still extant in the world.

We see this as well when the Rema discusses it in Shulchan Aruch, Orach Chaim, siman 426, seif 2, mentioned above in the summary:

שולחן ערוך אורח חיים סימן תכו
סעיף ב

ונוהגין לומר: דוד מלך ישראל חי וקיים, שמלכותו נמשל ללבנה ועתיד להתחדש כמותה וכנסת ישראל תחזור להתדבק בבעלה שהוא הקב"ה, דוגמת הלבנה המתחדשת עם החמה שנאמר: שמש ומגן ה' (תהילים פד, יב) ולכך עושין שמחות ורקודין בקידוש החדש דוגמת שמחת נשואין. (בחיי פרשת וישב וד"ע

A different base pasuk is cited, but the idea is the same, about malchut bet David, rather than David himself. My guess is that rather than any deep meaning involved in this, it is rather a statement drawn initially from the siman given in the gemara and possibly later invested with other meaning.

I also wonder if we might compare "David Melech Yisrael Chai veKayam" with the statements directed first towards Nevuchadnezzar and then towards Belshazzar, in sefer Daniel:

Daniel 3:9

ט עֲנוֹ, וְאָמְרִין, לִנְבוּכַדְנֶצַּר, מַלְכָּא: מַלְכָּא, לְעָלְמִין חֱיִי

9 They spoke and said to Nebuchadnezzar the king: 'O king, live for ever!

Daniel 5:10

י מַלְכְּתָא--לָקֳבֵל מִלֵּי מַלְכָּא וְרַבְרְבָנוֹהִי, לְבֵית מִשְׁתְּיָא עללת (עַלַּת); עֲנָת מַלְכְּתָא וַאֲמֶרֶת, מַלְכָּא לְעָלְמִין חֱיִי--אַל-יְבַהֲלוּךְ רַעְיוֹנָךְ, וזיויך (וְזִיוָךְ) אַל-יִשְׁתַּנּוֹ.

10 Now the queen by reason of the words of the king and his lords came into the banquet house; the queen spoke and said: 'O king, live for ever! let not thy thoughts affright thee, nor let thy countenance be changed;

This "live forever" is not meant literally but rather as a sort of "long live the king."