Translation:Shulchan Aruch/Orach Chaim/242

Even regarding someone who depends on others for his livelihood, if he has [even just] some [food] of his own, he must make an effort to honor the Shabbat. The halachic decisors [poskim] who said, "make your Shabbat as a weekday so that you not rely on others," only said it regarding one in a time of dire need. Therefore [a person who has a bit of their own food, i.e. the initial situation discussed,] must practice restraint during the week so that he can honor the Shabbat. This is based on the decree of Ezra, that poeple should wash clothes on Thursday (i.e. prepare during the week) for the honor of Shabbat. RAMA: We customarily knead a quantity of dough that is sufficient to become obligated in the mitzvah of challah, in the home. With these we bake breads that we will then break on Shabbat and holidays. This is one of the [many ways] in which we honor Shabbat and holidays, and one must not deviate from this custom. Some write that in a few places they are accustomed to eat mulitha, also known as pashtida, on the night of Shabbat as a remembrance to the manna, which was covered above and below. [Source: Maharil; Rama comments: I don’t see that one should be concerned to follow this.