Siman 482

The Rambam wrote at the end of the eighth chapter: One who has only a kezayit of guarded matzah, when he finishes his meal of matzah that is not guarded, he recites the blessing "on the eating of matzah" and eats that kezayit, and does not taste anything after it. Thus far his words, and according to the approach of the Rambam who requires guarding from the time of harvesting and for all the days of Pesach, as I have written in siman 453, see there. However, if he does not have such guarded matzah, it is obvious that we do not tell him not to eat during all the days of Pesach, for the entire essential requirement of guarding is from the words of the scribes, as the Rambam wrote in the fifth chapter. And according to Rashi and Tosafot, the guarding is "for its sake," and anything that is not "for its sake" is not called "guarded," as I have written there. And it is only for the first night.

And behold, the Rambam did not clarify when one should eat the maror and the "korekh." The Rif wrote that one should eat the maror after the kezayit of shemurah, and also perform "korekh." And the Tur, in the name of Rabbeinu Yonah, wrote that after the kezayit one should eat nothing; see there. If so, it follows automatically that one eats the maror beforehand. And even though one eats the maror before the matzah—we have no concern with this. This is the opinion of our teacher, the Beit Yosef, who wrote: One who has only a kezayit of matzah shemurah recites the blessing "on the eating of maror" and eats, and when he finishes his meal of matzah that is not shemurah, he recites the blessing "on the eating of matzah" and eats that kezayit. And he does not taste anything after it. Thus far his words. However, when he has two kezayitim—he should eat the first for "Hamotzi" and the second for the afikoman, and the "korekh" he should perform with the matzah that is not shemurah. And a sick person who cannot eat without a cooked dish—should eat the kezayit of matzah with the cooked dish. And if he can only eat a kezayit—he should eat at the beginning without matzah, and afterwards eat the kezayit, and recite the blessing "on the eating of matzah" (Magen Avraham), or he should eat matzah ashirah beforehand.

And one who has for the two nights only three matzot – he shall eat on the first night from one matzah, and eat "Hamotzi" and "Al Achilat Matzah" from it. And he shall leave two for the second night, so that he will have lechem mishneh for the second night. And it is simple that if the one does not suffice for all the kezayit measures – the first night takes precedence. (See the Taz who resolves the opinion of the Rosh, and it requires further study, see there. And nowadays the law of the dough of a non-Jew is not relevant at all, for we knead with yeast and it becomes chametz immediately. And in their days they would knead like thin cakes.)