The Gemorah records a debate among Chazal (Shabbos 70a) about why the Torah singled out the prohibitive mitzvah of creating fire on Shabbos – as opposed to the other 38 acts of labor. One Tanna opines havarah l’lav yatzas, havarah, kindling fire, was singled out to be a mere prohibition – not a capital crime. The other Tanna contends havarah l’chaleik yatzas, it was singled out to separate the melachos, forms of labor, into distinct categories of liability. Each melachah is an act of chillul Shabbos and carries with it its own punishment. If one performs two melachos, he is guilty of two separate offenses, and he is punished accordingly. The debate aside, the obvious question is: What is so special about kindling fire that it should be the one melachah, act of labor, to be selected to teach the lesson of havarah l’chaleik yatzas.
The Imrei Emes explains that Hashem prohibitred all other thirty-eight melachos, because He rested on the seventh day/Shabbos. He employed all these acts of labor in the Creation of the world and everything in it. There was one melachah from which Hashem did not rest: meleches havarah, because fire was not introduced until Motzoei Shabbos, when Adam rubbed two stones together and made fire. As such, we had no reason to assume that havarah would not be prohibited on Shabbos. Thus, the pasuk had to inform us that kindling fire on Shabbos is prohibited.
