Ḥol Ha-mo’ed is unique. At first glance, it would seem that after attaining an elevated state on Yom Tov, we should maintain it for the entirety of the festival. Nevertheless, after the first day(s) of Yom Tov we observe Ḥol Ha-mo’ed, and only at the conclusion of the festival do we return to the elevated state of Yom Tov. I will offer a brief explanation of the significance of this, based on the wonderful explanations of R. Natan, the disciple of R. Nachman of Breslov.
The Ba’al Shem Tov offers an analogy. When we begin to teach a child to walk, we help him out. Later, we let him try to stand and walk on his own. At first he falls, but eventually he succeeds. Similarly, at the beginning of a person’s spiritual ascent, heaven provides him with a great illumination, beyond his true level. Afterward, it is removed, and he falls. He must now work hard to hold on to what he has and resist any temptations. By doing so, he comes to earn the great illumination. This time he will not fall, because now he deserves it.
Based on this, we can understand what Ḥol Ha-mo’ed is all about. At the beginning of the festival God enlightens us with a great illumination – beyond what we deserve. When Yom Tov ends, He removes the light. Our job is to strengthen ourselves during Ḥol Ha-mo’ed, by studying Torah and enjoying the festival. With this strength, we earn the additional Yom Tov at the festival’s conclusion. Since we have prepared ourselves during Ḥol Ha-mo’ed, we are on a higher level. This idea accords with the statement of the Sages that the level which the Jews attained on the seventh day of Pesaḥ at the splitting of the Red Sea was greater than the level they had attained on the first day of Pesaḥ at the slaying of the Egyptian firstborn. Additionally, the Sages state that a maidservant at the sea saw things that Yeshayahu and Yeḥezkel were unable to see (Mekhilta, Beshalaḥ). At the end of Sukkot as well, there is extra joy when we celebrate Shemini Atzeret. This fits with the statement of the Sages (Sukka 55b) that for the first seven days of Sukkot, our rejoicing with God is shared with all the nations, while on Shemini Atzeret God celebrates with us alone (Likutei Halakhot, Ḥol Ha-mo’ed 1:1 and 2:1).
Another purpose is served by the spiritual descent from Yom Tov to Ḥol Ha-mo’ed. It allows for the uplifting of weaker souls, for whom the sanctity of Yom Tov is too overwhelming. Since Ḥol Ha-mo’ed is closer to a weekday, they can ascend during this time with the help of the mitzvot observed then: studying Torah, enjoying the festival, strengthening relationships with friends, and giving charity. An indication of our spiritual mission on Ḥol Ha-mo’ed can be seen in the type of melakha permitted then – melakha to avoid a loss. This alludes to the idea that these days are set aside to elevate lost souls. Melakha for the sake of the festival is permitted as well, which hints that through Ḥol Ha-mo’ed we can understand the meaning of the festivals and thus achieve the ability to absorb the great light of the last day(s) of Yom Tov (ibid., 3:4; 3:6; 4:3; 4:6).
There is yet another purpose to the days of Ḥol Ha-mo’ed. Since they have an aspect of weekday, their sanctity extends to, and is revealed in, the weekdays. It is important to note that the holier the day, the more recognizable the divine overflow, and the more sweeping the prohibition of melakha. In contrast, the farther one gets from divine bounty, the harder he must work and the more he must suffer to earn a living (as restitution for Adam’s sin). Our mission is to reveal God’s word in everything we do. By doing so, we begin a gradual process that will free us from the burden of making a living and enable us to work in a relaxed, joyful way for the sake of heaven (see 3:1 above).
Shabbat is the foundation of the sanctity of time. Its sanctity is eternal, going back all the way to the six days of creation. Therefore, it is forbidden to do any melakha on Shabbat. The Jews are commanded to extend this sanctity. First, the holiness extends to the days of Yom Tov, which are weekdays sanctified by the Jewish people and thus transformed into holy days (as explained in 1:3 above). Since the days of Yom Tov are sanctified by the Jews, it is permitted to engage in melakha necessary to provide Jews with food (okhel nefesh). However, this still leaves weekdays distant from holiness. For this reason, God gave us the days of Ḥol Ha-mo’ed, which are “intermediate days” when some work is permitted and some is prohibited. Through the work that we do then for the sake of heaven, holiness is extended to all the work we need to do during the weekdays throughout the year. This is the main sense of “repairing the world”; even work for a livelihood must also be for the sake of heaven – to repair the world and improve it, to increase charity, and to set aside time for Torah study. In this way we repair all 39 types of labor, so that they will no longer be associated with the sin and punishment that make people subordinate themselves to materialism. Rather, they will be sanctified to establish a dwelling and home for the presence of the Shekhina (Likutei Halakhot, Ḥol Ha-mo’ed 4:8).