A common feature of the Aron, the Shulchan and the Mizbei’ach HaZahav in the Mishkan was that each had what the Torah calls a “Zeir Zahav Saviv,” “a golden diadem all around.” The Gemara in Yoma (72b) cites in the name of Rav Yochanan that Aharon HaKohen was Zocheh to acquire the Mizbei’ach and David HaMelech was Zocheh to acquire the Shulchan, but the Aron is still free for the taking, and anyone who wishes can acquire it. Rashi there comments that the Shulchan represents Keter Malchut, the Mizbei’ach represents Keter Kehunah, and the Aron represents Keter Torah. (This notion of the three crowns is also expressed by Rambam at the beginning of the third Perek of Hilchot Talmud Torah, where he says that Bnei Yisrael were given these three crowns of Malchut, Kehunah, and Torah.) These designations are appropriate because of the deeper ideas behind each of the three.
The Shulchan which held the Lechem HaPanim symbolized sustenance and an abundance of food. Ramban explains that after Beriat HaOlam, nothing was created Yeish MeiAyin, “something from nothing”; rather, the world operates in accordance with the natural laws that Hashem established. Therefore, in order to receive blessing, something physical must exist on which the Berachah can rest, and the Lechem HaPanim served as an object to which the Berachah of abundance and sustenance attached itself. Similarly, it is the job of a king, the leader of a nation, to prevent starvation and to make sure that his people have enough food to eat. Therefore, the Shulchan is the Kli in the Mishkan used to signify Bnei Yisrael’s Keter Malchut.
The Mizbei’ach HaZahav was used for the Ketoret that was offered daily, and along with the lighting of the Menorah, the burning of the Ketoret was one of the only tasks performed specifically by Aharon HaKohen. Thus, the Mizbei’ach HaZahav, which had a direct connection to Kehunah, was used to symbolize the Keter Kehunah.
Finally, the Aron, which rested in the Kodesh HaKadashim, housed the Luchot and therefore embodied the Keter Torah.
In differentiating between the various Ketarim, Rabbeinu Bachya points out that regarding the construction of the Zeir Zahav for the Shulchan and Mizbei’ach HaZahav, the Torah uses the language “VeAsita Lo,” while for the Aron the Torah says “VeAsita Alav.” The Lo by the Shulchan and Mizbei’ach hints to the idea that the Zeir Zahav was made for a specific person, and indeed Malchut can only be obtained by a descendant of David Hamelech, while Kehunah can only be inherited by a descendant of Aharon HaKohen. However, the VeAsita Alav of the Aron implies that the Zeir Zahav was made for the Aron itself and for what the Aron represents – Torah. The Midrash explains that indeed the Keter Torah is on a higher level than the Ketarim of Malchut and Kehunah, and one who acquires the Keter Torah is considered to have obtained all three Ketarim, even if he is not a descendant of David or Aharon. This is what the Gemara means by saying that no one took the Aron and that it is still available for anyone who wants it; Torah is ready for anyone to attain, regardless of family background or social class, and one who does attain the Keter Torah is viewed as being above even the kings and Kohanim. Indeed, Hashem set forth for all of Am Yisrael to be a “Mamlechet Kohanim,” even those who cannot be kings or Kohanim due to lineage.
However, the Mishnah in Avot (4:12) writes that there are the three Ketarim of Torah, Kehunah, and Malchut, but the Keter Sheim Tov rises above them all. What exactly is the Keter Sheim Tov, and how does one acquire it? Additionally, if there are indeed only three crowns, then why does it seem like there is a fourth?
Rashi, in his commentary to this Mishnah, defines a person with a Sheim Tov as one who only performs positive actions. On the Pasuk from Kohelet (7:1), “Tov Sheim MiShemen Tov,” “A good name is better than good oil,” he explains that Chananiah, Mishael, and Azaryah, who were saved from the Kivshan HaEish, were better than Nadav and Avihu, who were killed by fire when they offered uncalled-for Ketoret. This is true because Chananiah, Mishael, and Azaryah performed Maasim Tovim, which supercedes Nadav’s and Avihu’s having been anointed with the Shemen HaMishchah. Rashi further explains that one who acquires all three Ketarim is given the Keter Sheim Tov, which represents the completeness of the person.
Based on the Midrash and the Mishnah in Pirkei Avot, one who obtains the Keter Torah, and thus the Keter Malchut and Keter Kehunah as well, is consequently given the Keter Sheim Tov. This is because one who truly acquires Torah allows it to permeate him and control his actions and decision-making, thereby ensuring that everything he does is good. It is quite appropriate for this ultimate crown to be named the Keter Sheim Tov, for a person who only does Maasim Tovim and patterns his life after the paradigm set forth by Torah and Halacha is praiseworthy and can be noted as truly having a Sheim Tov.