The Prohibition against Melachah on Shabbat and Yom Tov
You should not kindle a fire in any of your dwellings on the Shabbat. (Shemot 35:3)
This pasuk tells us that one may not kindle a fire on Shabbat. In other words, this pasuk informs us that creating fire – havarah – is one of the thirty-nine forms of melachah – creative work – prohibited on Shabbat. It is odd that the Torah finds it necessary to specify this melachah. The thirty-nine melachot are not enumerated in the Torah. Instead, they are derived from the Mishcan – the Tabernacle. Those functions that were fundamental to the construction of the Mishcan are included among the melachot. Havarah is one of these functions. Therefore, it seems reasonable that the kindling of fire should be one of the melachot. We should not need a special passage to inform us that havarah is a melachah. Why does the Torah specifically prohibit this melachah?
The commentaries offer a number of responses to this question. Rabbaynu Ovadia Sforno suggests that havarah lacks one of the basic requirements necessary for an activity to be defined as a melachah. All melachot are creative activities. For example, the melachah of writing results in written letters. The melachah of sewing produces stitches. Kindling a flame is fundamentally destructive. The fuel is burned and consumed by the fire. It is not at all obvious that havarah should be included among the melachot. Therefore, the Torah specifies that creating fire is melachah.
Nachmanides offers a different explanation for our pasuk. In order to understand his comments, some background is required. Shabbat is not the only occasion on which melachah is prohibited. It is also prohibited to perform melachah on Yom Tov – a festival. However, the prohibition on Yom Tov does not include all of the thirty-nine melachot. Those melachot that are related to ochel nefesh – those melachot that provide personal pleasure – are permitted. For example, it is permitted to cook on Yom Tov. This is because food provides personal enjoyment. Havarah is permitted on Yom Tov. This activity also is performed for the purpose of personal pleasure and is considered a melachah of ochel nefesh. Why are melachot of ochel nefesh permitted on Yom Tov? One of the fundamental differences between Shabbat and Yom Tov is that the observance of Yom Tov includes a requirement simchah – happiness. In order to enable us to achieve this state of simchah, the melachot of ochel nefesh are permitted. The observance of Shabbat does not include an obligation of simchah. Nachmanides explains that our passage tells us that kindling fire is prohibited on Shabbat. This pronouncement teaches that the prohibition of melachah on Shabbat differs from the Yom Tov prohibition. On Shabbat, all thirty-nine melachot are prohibited. Even the melachot of ochel nefesh are included in the Shabbat prohibition.
Nachmanides further explains that it is not obvious that melachot of ochel nefesh should be included in the prohibition against melachah on Shabbat. Although the obligation of simchah does not extend to Shabbat, we are obligated in oneg – experiencing joy – on Shabbat. It is reasonable to assume that this obligation of oneg on Shabbat has a similar impact as the obligation of simchah on Yom Tov. We would expect the obligation of oneg to dictate that melachot of ochel nefesh should be permitted on Shabbat. This is the lesson of our passage. Despite the obligation of oneg on Shabbat, all thirty-nine melachot are prohibited – even those of ochel nefesh.
Nachmanides does not discuss one important question. As explained above, the obligation of oneg on Shabbat is similar to the requirement of simchah on Yom Tov. Because of the obligation of simchah, those melachot related to ochel nefesh are not prohibited on Yom Tov. Why does not the obligation of oneg on Shabbat have the same impact? Why are the melachot of ochel nefesh prohibited on Shabbat?
Before answering this question, it is important to note that the sanctity of Yom Tov and Shabbat is expressed through the prohibition against melachah. All occasions that the Torah describes as sacred are characterized by this prohibition. Therefore, the melachah prohibition is elemental to the definition and character of these days. Our question suggests that there is a basic difference between the obligation of simchah on Yom Tov and oneg on Shabbat. Simchah is not merely an activity in which we engage on Yom Tov. The obligation of simchah – like the melachah prohibition – is part of the definition or character of Yom Tov. Yom Tov is defined as a period of simchah. The requirement to refrain from the performance of melachah must be formulated in a manner that is consistent with and accommodates the simchah element of Yom Tov observance. Therefore, it is impossible for the Yom Tov prohibition of melachah to include the melachot of ochel nefesh. The inclusion of these melachot would be result in an inconsistency in the fundamental character of the Yom Tov.
Oneg is an obligation on Shabbat. However, it is not part of the basic definition or character of the day. In other words, oneg is an activity that we perform on Shabbat. It is not elemental to the character of Shabbat. Therefore, the prohibition on Shabbat of the melachot of ochel nefesh does not contradict the nature or definition of Shabbat. Instead, the obligation of oneg must be fulfilled in a manner that accommodates the sanctity and character to Shabbat. It must be fulfilled without performance of those melachot associated with ochel nefesh.
An analogy will help understand this distinction. A clothing designer is considering fabrics and colors for a suit under design. He envisions a man’s suit that will be worn on formal occasions. He chooses a dark wool fabric for the basic design. He then decides he should bring another subtle color into the design and adds a maroon windowpane pattern. Notice that the basic color for the suit was selected based upon the function for which the suit was designed. The second color was selected to enhance the primary one. Similarly, oneg – like the maroon of the suit – is an enhancement; it is not elemental. Therefore, it is observed in a manner that is consistent with the melachah prohibition. In contrast, the obligation of simchah on Yom Tov is comparable to the designer’s vision of the suit’s use. This purpose is fundamental to the suit’s design; its color is selected to accommodate this objective. So too, the Yom Tov melachah prohibition is designed to accommodate the requirement of simchah.
Moshe’s Suspension of Contributions for the Mishcan
And Moshe gave orders to make an announcement in the camp, “Let no man or woman bring any more material for the sacred offering.” (Shemot 36:6)
The nation responded to the request for donations of materials for the construction of the Mishcan. These donations were sufficient for creating the Mishcan and all of its components. The craftsmen charged with the fashioning of the Mishcan reported to Moshe that they had received sufficient material. Upon receiving this news, Moshe announced that no more donations should be brought. The commentaries remark that an exact tally was kept of the donations. The purpose of this accounting was twofold. First, it was essential to secure sufficient materials. Second, Moshe did not wish to collect more than was needed. The importance of collecting sufficient materials is obvious. However, the above pasuk emphasizes that Moshe was equally concerned with not collecting excess materials. Once the needed materials were donated, Moshe immediately directed Bnai Yisrael to stop bringing donations. Why was this issue so crucial? Why was Moshe so deeply concerned with not accepting excess donations?
The commentaries offer various explanations. We will consider one of these responses. Gershonides explains that Moshe’s concern was based on a principle found in the Talmud. The Talmud in Tractate Ketubot explains that a person should not donate more than one fifth of one’s assets to charity. Maimonides extends this principle to the performance of all mitzvot. A person should not spend more than one fifth of his wealth on the performance of any mitzvah. For example, in purchasing an animal for sacrifice, this limit applies. Maimonides offers an explanation for this restriction. A person should avoid being dependant on others for support. Therefore, one should not risk impoverishing himself. Gershonides explains that Moshe’s concern was based on this principle. He did not want the people to bring more than was needed. He did not want anyone to become impoverished out of zeal to contribute to the Mishcan.
Gershonides offers an important insight into the restriction against spending an excess of one fifth of one’s wealth in the performance of a mitzvah. He agrees with Maimonides’ explanation of the restriction. One should not risk poverty and lose of independence. However, Gershonides asserts that there is a more fundamental explanation of the restriction. He explains that the Torah prohibits the performance of a mitzvah in a manner that leads to evil. Becoming impoverished through contributing to charity or performing a mitzvah is a negative or evil outcome. Gershonides further explains that such an evil outcome discourages others from performing the mitzvah.  Rabbaynu Ovadia Sforno, Commentary on Sefer Shemot 35:3. Rabbaynu Moshe ben Nachman (Ramban/Nachmanides), Commentary on Sefer Shemot 35:3.  Mesechet Ketubot 50a.  Rabbaynu Moshe ben Maimon (Rambam/Maimonides) Mishne Torah, Hilchot Erchin VeCharamin 8:13.  Rabbaynu Levi ben Gershon (Ralbag/Gershonides), Commentary on Sefer Beresheit, (Mosad HaRav Kook, 1994), p 444.