1) Gentiles have no obligation to abide by the laws of Shabbat; there are three different reasons, given by the Rishonim (early Talmudic authorities - approx 900-1500 C.E), as to why the Sages enacted the prohibition against asking a Gentile to perform a prohibited activity on Shabbat: a) So that Jews will not take the prohibitions of Shabbat lightly, and end up violating the Shabbat themselves (Rambam, Laws of Shabbat, 6:1); b) There is a Rabbinic restriction, based on a verse in Isaiah (58:13), which forbids discussing, on Shabbat itself, one's business affairs, weekday concerns, or any of the 39 categories of prohibited activity. Instructing a Gentile on Shabbat to perform a Melacha would be a violation of that Rabbinical prohibition; c) In Jewish law, one's agent is the equivalent of oneself (except when the agent is committing a crime). The Sages extended this concept to include a case of a Jew enlisting a Gentile to perform Melacha for him on Shabbat, making it tantamount to the Jew doing the Melacha himself. All three reasons have been accepted by Halachic authorities, and all three must be applied to each case. Therefore, one may not ask a Gentile on Shabbat, or even during the week to perform a Melacha for him on Shabbat. Applying reason (b), one may not even ask a Gentile on Shabbat to perform a Melacha for him after Shabbat. 2) There are certain circumstances in which one is allowed to ask a Gentile to perform a prohibited activity on Shabbat (sometimes, one may only ask him to perform an act which is prohibited Rabbinically, not Biblically). One of those circumstances is for someone who is ill, even though there is no danger to life (the definition of ill in this case is someone who is either bedridden or suffering from something which weakens the entire body, like a migraine); one may ask a Gentile to perform even a Biblically prohibited activity on Shabbat, for the sake of an ill person. This leniency applies even when a person is not yet ill, but would be in danger of becoming ill if the Gentile doesn't perform the act. Therefore, if a house is very cold on Shabbat, and there is a danger that people will become sick, one may ask a Gentile to turn on the heater. 3) There are certain circumstances in which a Gentile may be asked to perform a Rabbinically prohibited act in order to warm up food which is essential to the Shabbat meals. 4) One who has a desire to go beyond the ''letter of the law''.

1) ''Zoreah'' - sowing (seeds). Planting seeds in the ground on Shabbat is a violation of the Av Melacha (prototype prohibited activity called ''Zoreah''. Since the purpose of sowing seeds is to cause them to grow, any activity which causes growth, like watering plants or seeds, would be prohibited as a Toldah (derivative) of the Melacha of ''Zoreah''. The Mishna Berurah (336:26) quotes other authorities who rule that pouring liquid on soil is also a derivative of the Av Melacha called ''Choresh'' (ploughing), because it serves to soften the soil. According to this opinion, it would even be prohibited to pour water onto soil that hasn't yet been sown. 2) See Chapter 83.

השופך משקים במקום שהקרקע מצמחת חייב משום זורע שהרי המשקה גורמת שתצמח הקרקע ועל כן יש ליזהר מלאכול בגינה כי בקושי יכול ליזהר שלא לשפוך משקים על הארץ ומלבד זאת יש בגינה איסור טלטול

1) It's forbidden to squeeze out liquid from the fabric in which it is absorbed (See Laws 12 and 15 above). When one wipes up a spill with a sponge that has no handle, it is inevitable that one will end up squeezing out some liquid while one is holding the sponge; however, when the sponge has a handle, squeezing out liquid is not inevitable (Rambam, Rashi). The Ra'avad claims that even with a handle, it is inevitable that liquid will be squeezed out, but since it is not the usual way of extracting liquid, it is permitted (See Mishna Berurah 320:47).