1)

(a)The source for the Lav of Mechamer on Shabbos is the Pasuk in Yisro - "Lo Sa'aseh Kol Melachah Atah ... u'Vehemtecha".

(b)We counter the suggestion that this is a source for saying that an Aseh is not Docheh a Lo Sa'aseh - on the grounds that the Lavin of Shabbos are different, because Shabbos is generally more stringent.

(c)We refute this argument however, from another Beraisa which rules that if a father orders his son fetch something from a Beis ha'Kevaros (if he is a Kohen) or not to return a lost article (even if he is a Yisrael) - the son is forbidden to obey him.

(d)And he learns this from the Pasuk in Kedoshim "Ish Imo v'Aviv Tira'u, v'es Shabsosai Tishmoru ... ", which indicates that the father is as much obligated to honor Hash-m (i.e. to observe the Shabbos) as is the son ('Kulchem Chayavim bi'Chevodi'), in which case he has no authority to override Hash-m's commands ...

(e)... a proof that we can learn other Mitzvos from Shabbos, despite the fact that Shabbos is more stringent.

2)

(a)We reinstate the first Beraisa by other Melachos of Shabbos ('Sh'chot Li' 'Basheil Li'), and we reject the earlier suggestion to learn Aseh Docheh Lo Sa'aseh she'Yesh bo Kares from the second Beraisa, and from "Alehah", that Achos Ishah is Patur from Yibum, because the second Beraisa is speaking about Hechsher Mitzvah - meaning that, in the current situation, there is no other way of observing it other than by breaking the Shabbos, whereas in the case of Achos Ishto, one has the option of performing Chalitzah, in which case "Alehah" would not be required to forbid Yibum.

(b)We repeat the entire Sugya, switching the Mitzvah of Kibud Av with that of Mora Mikdash ("es Shabsosai Tishmoru u'Mikdashi Tira'u" [also in Kedoshim]). We initially interpret "u'Mikdashi Tira'u" - with reference to building the Beis ha'Mikdash, which be permitted if not for this Pasuk.

(c)We counter the argument that we cannot learn Yibum (Achos Ishto) from Binyan Beis-Hamikdash, because the latter is a Hechsher Mitzvah - on the grounds that we already know that from Kibud Av va'Em.

(d)And we refute the proof from there that Aseh Docheh Lo Sa'aseh she'Yesh bo Kares by changing the Limud of "es Shabsosai Tishmoru u'Mikdashi Tira'u" - to the fact that just as one respects, not so much the Shabbos, as the One who ordained it, so too, must one respect, not the Beis-ha'Mikdash, but the One who ordered it to be built.

3)

(a)Respect of the Beis-Hamikdash incorporates not entering the Beis ha'Mikdash with any one of four things, including one's staff and one's shoes - one's money-belt and the dust on one's feet (as we learned in Berachos).

(b)Nor may one use the Beis Mikdash as a Kapandriya - (a short-cut).

(c)We learn the prohibition of spitting there from a 'Kal va'Chomer - from the prohibition of entering the king's palace wearing sack-cloth, which is not disgusting; how much more so spitting, which is.

(d)We know that Mora Mikdash applies even nowadays (when the Beis ha'Mikdash is not standing) - from the Pasuk "es Shabsosai Tishmoru u'Mikdashi Tira'u"; just as observing Shabbos applies at all times, so too, does respecting the Beis Hamikdash.

4)

(a)So we try to learn Aseh Docheh Lo Sa'aseh she'Yesh bo Kares from 'Hav'arah'. According to Rebbi Yosi, the Pasuk in Vayakhel singles out the Melachah of "Lo Seva'aru Esh b'Chol Moshvoseichem" to reduce making a fire on Shabbos from a Chiyuv Kares to an ordinary Lav. In Rebbi Nasan's opinion - it comes to divide the Melachos into thirty-nine separate entities (to be Mechayev Sekilah [or a Chatas - see Chochmas Shlomo] for transgressing even one of them).

(b)"b'Chol Moshvoseichem" means - wherever you live, even in Chutz la'Aretz.

(c)The problem with this is - that Shabbos is a personal obligation (that has nothing to do with the land) which automatically applies everywhere, rendering the words superfluous.

5)

(a)To answer this question, we cite a Talmid quoting Rebbi Yishmael, discussing the Pasuk in Ki Setzei "v'Chi Yiheyeh b'Ish Chet Mishpat Ma'ves v'Humas" - which either means even on Shabbos (precluding Misas Beis-Din from the Lav of "Mechalelehah Mos Yumas"); or it means specifically on a week-day (in which case "Mechalelehah Mos Yumas" incorporates Misas Beis-Din).

(b)Rebbi Yishmael solves the dilemma by means of the 'Gezeirah-Shavah' "Moshvoseichem" (here) from "v'Hayu Eileh Lachem l'Chukas Mishpat l'Doroseichem b'Chol Moshvoseichem" - which teaches us that just as the latter is referring to Beis-Din, so too, is the former (where it writes "Lo Seva'aru").

(c)By establishing Rebbi Yishmael like Rebbi Nasan (who holds that Hav'arah, like other Melachos on Shabbos, is Chayav Kares), we try to prove - that, if not for "Lo Seva'aru", Beis-Din would kill on Shabbos, a proof that "Aseh Docheh Lo Sa'aseh she'Yesh bo Kares.

6)

(a)We counter that, even if the author was Rebbi Yosi, the proof would still be valid - because he only considers making a regular fire a Stam Lav, but not killing by burning, which entails boiling a lead wick until it melts (which is a real Melachah, even according to him) ...

(b)... because what is the difference between boiling a lead wick and boiling dyes (which is the source for the Melachah of cooking on Shabbos).

(c)Rav Shimi bar Ashi rejects the proof. If not for the Pasuk and the 'Gezeirah-Shavah', he says, Misas Beis-Din would override Shabbos, not because of the principle 'Aseh Docheh Lo Sa'aseh' - but due to a 'Kal va'Chomer' from Avodah (as we shall now proceed to explain).