1) Even though the act of cooking is one of the 39 types of creative work which are forbidden to be performed on Shabbat, if something is placed on the flames or in the oven before Shabbat, it is Biblically permissible to allow the cooking process to continue by itself on Shabbat. However, the Sages prohibited allowing uncooked food, placed on the flames on Friday afternoon, to remain on the flames after sunset, because they were concerned that one may come to stir the coals (or, in modern times, adjust the flame) on Shabbat in order to speed up the cooking process, thereby desecrating the Shabbos in two ways - through the act of cooking and the act of igniting the coals. This Rabbinical prohibition was established only for conditions in which it is reasonable to suspect that one might attempt to speed up the cooking process by increasing the heat. Hence, it would be permissible to leave food on the flames or in the oven, to continue cooking or to retain its heat on Shabbos, if, for example, the food was fully cooked (or, according to some, just edible) by the time Shabbat arrived, or if one did something to eliminate the likelihood of stirring the coals, such as removing them, or covering them (with ashes, or, in modern times, with a metal sheet called a ''blech''), or even sealing the oven door shut (so that one needed to exert some effort to open it). There are many criteria governing whether it would be permissible to allow food to remain on the flames or in the oven after Shabbat comes in, and consequently, one would have to consult a detailed book about the Laws of Shabbat in order to determine the practical application of the law in each individual circumstance. In Halacha 18 appearing above, the Kitzur Shulchan Aruch is discussing a case in which the food is already edible by the time Shabbat arrives, and therefore, we are not concerned that one will attempt to speed up the cooking process in order to have the food ready to eat on Friday night. Consequently, there is no need to seal the oven door shut. In Halacha 19, the Kitzur makes it clear that if the food is not going to be edible by sunset, it would be prohibited to let it remain in the oven after Shabbat arrives, unless one sealed the oven door shut, thereby eliminating the risk that one might adjust the oven flames (In all these cases, we are concerned that one may momentarily forget that it is Shabbat and adjust the flames. The Sages were confident that in the time it takes to pull open a sealed oven door, one will remind oneself that it is Shabbat, and will refrain from adjusting the heat).

1) ''kitniot'' small (from katan) seeds or beans. 2) Items made from or inside dough, i.e pastries or pies.

הא דמותר להטמין גם כשאין התנור טוח בטיט זהו דוקא כשמטמינין בשר וכן אפילו כשמטמינין מיני קטניות ומיני בצק אלא שמטמינים זמן הרבה קודם הלילה באופן שיוכל להתבשל קודם הלילה קצת עד שיהא ראוי לאכילה על ידי הדחק אבל כשמטמינין מיני קטניות ומיני בצק סמוך ללילה צריכין דוקא לטוח התנור בטיט כי מן הסתם אינו גרוף וקטום כראוי וצריכין ליזהר בזה כי אם לא עשו כן אז אפילו בדיעבד המאכלים אסורים עד למוצאי שבת בכדי שיעשו

1) One of the 39 categories of creative work prohibited on Shabbat is ''Demolishing'' (Soter) - in other words, taking apart a structure for a constructive purpose. This prohibition only applies to demolishing a structure that was designed to stay together permanently; the case in our Halacha involves an oven door which was sealed only temporarily, that is, until the food in the oven would be needed on Shabbat, and consequently, the act isn't even prohibited Rabbinically. However, because it closely resembles an act of demolishing, we do our best to avoid carrying out the task ourselves. (Mishna Berurah 259:19-22) 2) It should be noted that if there are still coals burning in the oven, it is prohibited for a Jew to open the oven door (whether sealed or unsealed) on Shabbat, because the resultant draft of air will further ignite the coals. (Mishna Berurah 259:22) 3) An act that is part of one of the 39 categories of creative work prohibited on Shabbat, only becomes Biblically prohibited if it is performed in its usual manner. Those authorities who are concerned that opening a sealed oven door might be considered an act of demolishing, require the use of a ''Shinui,'' that is, some divergence from the way the act is normally performed, in order to avoid the problem.