1) וַיֹּ֣אמֶר מֹשֶׁ֔ה אֶל־כׇּל־עֲדַ֥ת בְּנֵֽי־יִשְׂרָאֵ֖ל לֵאמֹ֑ר זֶ֣ה הַדָּבָ֔ר אֲשֶׁר־צִוָּ֥ה ה׳ לֵאמֹֽר
Rashi comments: זה הדבר אשר צוה – לי, לאמר – לכם. Moshe was telling Bn"Y that Hashem had spoken to him and he was charged with the task of conveying the information to them. Isn't that how every mitzvah in the Torah was given? (See the meforshei Rashi)
I found a pshat in a sefer called Ramat Shmuel by one of the chachmei Morocco that fits the words very nicely. Moshe was about to ask Bn"Y for donations for the mishkan. When the Rabbi or the President of the shul makes an appeal for some cause and people give, sometimes they feel like they are giving because the Rabbi or President twisted their arm, or gave a great speech, or maybe they like the Rabbi or think it really is a great cause. Moshe said to Bn"Y that he doesn't want to hear any of that. "Don't say I am giving because of Moshe." Rather, Moshe said, וַיֹּ֣אמֶר מֹשֶׁ֔ה אֶל־כׇּל־עֲדַ֥ת בְּנֵֽי־יִשְׂרָאֵ֖ל, that לֵאמֹ֑ר, to say when you give: זֶ֣ה הַדָּבָ֔ר אֲשֶׁר־צִוָּ֥ה ה׳ לֵאמֹֽר "This is what Hashem told Moshe to say." It's not my arm twisting, the cause is not my idea, don't give because you like me -- I'm just the middleman. It all comes from Hashem; it's His message.
R' Shimon Sofer says a similar pshat. Chazal extol the virtues of someone who motivates others to give even more than someone who just gives himself. Moshe did not just want people to give, but לֵאמֹ֑ר, tell others about it, tell others זֶ֣ה הַדָּבָ֔ר אֲשֶׁר־צִוָּ֥ה ה׳ לֵאמֹֽר, so that word gets out and they will be motivated as well.
2) The parsha singles out for mention the issur of lighting a fire on Shabbos. לֹא־תְבַעֲר֣וּ אֵ֔שׁ בְּכֹ֖ל מֹשְׁבֹֽתֵיכֶ֑ם בְּי֖וֹם הַשַּׁבָּֽת. The meforshim offer various reasons in pshat why this issur in particular was singled out, and why davka here when the mitzvah of Shabbos had been given earlier (see R' Chaim Kanievski in Taama d'Kra). Rashi quotes the halachic derush of Chazal: יש מרבותינו אומרים (בבלי שבת ע׳.): הבערה ללאו יצאת, ויש מהן אומרים: לחלק יצאת. One view is that this is the source for the rule that you are chayav a chatas on each individual melacha done on shabbos and you don't have to violate all 39 at once to be chayav for chilul shabbos. The other view is that lighting a fire is an exception and is only an issur lav, not kareis/chatas.
Yesh lachkor: according to the view that hava'ra is a lav, does that mean it is not one of the 39 melachos, or it is a melacha, just it has a lesser punishment?
Nafka minos:
1) Would the hasra'ah for violating hava'ra be "lo taaseh kol melacha" (putting aside the Minchas Chinuch's discussion of whether one needs to include the specific melacha being violated in the hasra'ah), or would it be "lo tiva'aru eish?"
2) Is there an issur of hava'ra on Yom Tov? The 39 melachos carry over to Y"T, but if hava'ra is a seperate issur, maybe not (similar question is asked about the issur of shevisas b'heima.)
The gemara in Pesachim (5a-b) quotes R' Akiva as proving that "ba'yom ha'rishon tashbisu chametz" must mean erev Pesach and not the first day of chag because burning one's chametz on Y"T itself is assur.
רבי עקיבא אומר אינו צריך הרי הוא אומר אך ביום הראשון תשביתו שאור מבתיכם וכתיב כל מלאכה לא (תעשו) ומצינו להבערה שהיא אב מלאכה
The gemara deduces from this proof that R' Akiva holds that hava'ra is singled out l'chaleik, not because it is a lav. How do we see that from the proof? Rashi explains that since R' Akiva refers to hava'ra as an אב מלאכה, it must be the same as any of the other 39 melachos. Tos quotes a Riv"a that the proof is from the fact that hava'ra is prohibited on Y"T. Had it been a lav, it would be a specific din in hil shabbps (point 2 above).
Why didn't Rashi accept the interpretation of Riv"a? It could be that according to Rashi the din הבערה ללאו יצאת just means the punishment is diminished, but hava'ra still has a shem melacha and therefore would be assur on Y"T too.
Rabeinu Chananel has a different pshat entirely in the sugya. He writes that R' Akiva must hold havra'ra is like any other melacha because if הבערה ללאו יצאת the mitzvas aseh of biur chametz would be doche the lav and it would be allowed on Y"T. This just begs the question -- even if hava'ra is a melacha like any other, why isn't the aseh of biur chametz doche the lav of doing melacha? And if you tell me it's because on Y"T there is not only a lav but an aseh of shabbason as well that goes with it, why can't you say the same thing if הבערה ללאו יצאת and there would be no dechiya?
The R'Ch apparently holds (this is the shitas haRashba in Yevamos 6) that the aseh of shabbason only goes hand in hand with items that fall in the basket of the issur melacha of Y"T. It does not come into play when dealing with other issurim, whether it is mechamer achar be'hemto, or the lav of hava'ra.