See most answers to question to 35:3:1.

R. Bachye: Whereas the former refers specifically to the prohibition against building the Mishkan, the latter pertains to all Melachos in general, which it presents in the form of making a fire, seeing as most Melachos are performed with fire. ¹

Rashi #1 and Ramban #1 (citing Shabbos, 70a, according to R. Yossi): To teach us that lighting a fire is only a La'av and is not subject to Kareis.

Rashi #2 and Ramban #2 (Ibid.), according to R. Nasan): To teach us that one is Chayav on Shabbos for each Melachah that one transgresses - and not only if one transgresses all thirty-nine.

Ramban #3 and Rashbam: To teach us that the prohibition of Melachah on Shabbos extends even to Ochel Nefesh ¹ (to lighting a lamp, wrapping food to preserve its heat and making a fire for warmth, all of which provide direct benefit - Ramban citing the Mechilta).

R. Bachye: Refer to 35:3:0.1:2.

Seforno: To teach us that one is Chayav, ² even though lighting a fire is normally a Kilkul (destructive), for which one is generally Patur on Shabbos,

Moshav Zekenim #1 (citing B'chor Shor), Da'as Zekenim and Hadar Zekenim: Becouse lighting a fire does not seem seem to be a Melachah (and people would therefore say, 'Let us make a fire or prepare coals on Shabbos, so that we can work in gold and silver after Shabbos' - Da'as Zekenim and Hadar Zekenim).

Moshav Zekenim #2 (citing the Rosh): Because it is a Melachah that everyone needs to perform

Erech Apayim 2 (va'Yosef Avraham 5, citing the Zohar): Because "Eish" refers to anger, and even though it is always forbidden, on Shabbos one may not display anger on one's face [even if one feels calm].

Shabbos, 11b: It hints at conflagration - the punishment for Chilul Shabbos. ³ 10: Shabbos, 20a: Refer to 35:3:2:1.

R. Bachye: Because whereas there he was speaking to the elite of Yisrael, to whom he taught the inner serets of Shabbos, here he was addressing the whole of Yisrael - the men and the women, to whom he was not willing to teach the upper secrets of Shabbos, only the simple explanations of Shabbos, briefly. ¹

Shabbos, 20a: To extrapolate that one may light a fire to burn the limbs and the fat-pieces that go on the Mizbe'ach. ¹

Yevamos, 6b: To teach us, via a Gezeirah Shavah from Bamidbar, 35:29 "V'hayu Eileh Lachem le'Chukas Mishpat le'Doroseichem", that just as 'Moshvos' there is referring to Beis-Din, so too, here, and that consequently, Misas Beis-Din (S'reifah) does not override Shabbos. ²

Yerushalmi Beitzah, 5:2: To extrapolate that on Yom-Tov on is permitted to light a fire. ¹

Mechilta: To extrapolate that one is permitted to light a fire on Erev Shabbos even though it continues to burn on Shabbos. ²

Moshav Zekenim: Because, since the Torah does not write 'Kol ha'Oseh Kol Melachah Yumas', it cannot be coming to teach us about the Klal.