Why does the Torah juxtapose the Parshah of the half-Shekel to that of the Ketores?
Ba'al ha'Turim: The Torah juxtaposes Ki Sisa to the words "al Karnosav" - in the previous Pasuk to hint - to hint at what the Gemara states in Bava Basra, 10b 'Ramah Karno shel Yisrael be'Chi Sisa' (Hashem rised the strength of Yisrael through Tzedakah).
Oznayim la'Torah: Because like the Machtzis ha'Shekel, the Ketores has the power to stop plagues. 1
Oznayim la'Torah: As we find in Korach, Banidbar, 17: 11.
What is the meaning of "Ki Sisa"?
Rashi, Targum Onkelos and Targum Yonasan: It means 'When you decide to receive their total number'. 1
Moshav Zekenim, (and mostly in Hadar Zekenim citing Bereishis Rabah): Moshe asked that Hashem promised that Avraham's seed will not be able to be counted! Hashem said, in order to know the number, Tisa Es Rosh Bnei Yisrael, i.e. take the Gematriya of the first letters of the names of the Shevatim. It is 597, for Levi is not counted (from 20 years, rather, from one month); there were 597,000 Yisraelim, after deducting 3000 who died after Chet ha'Egel. 2
Hadar Zekenim #1: Refer to 30:12:4:2.
Hadar Zekenim #2: See the dearness of Yisrael! If they are elevated through (Machatzis ha'Shekel, which came through) an Aveirah, how much the more so they are elevated through their merits! 3
Oznayim la'Torah: The word "Sisa" itself translates as 'count'. 4
This implies that Moshe's main objective was to count the people and that the money that he received he used to manufacture the sockets. The Rashbam however explains, that his main objective was to collect money for the Mishkan, and he used the opportunity to count the people. (EC)
After deducting 3000, there were still an extra 3550! It says (32:24) that the Leviyim killed about 3000 people. Perhaps the others died through the plague or drinking water in which the dust of the Egel was strewn. However, when did Hashem say this to Moshe? If it was before Chet ha'Egel, the 3000 did not die yet! If it was after Chet ha'Egel, the count was 603,550 even after they died! (PF)
Yosef's brothers sold him, and through this, he fed the world. "Va'Yeshvu Le'echol Lechem" (Bereishis 37:25) - Leha'achil (to feed). If their Aveirah caused the world to live, how much the more so their merits!
Oznayim la'Torah: As we find in Matos, Bamidbar, 31:25.
What are the implications of the word "Venasnu Ish Kofer Nafdsho"?
Bartenura in Shekalim (1:3): To preclude women from the current half-Shekel donation.
Why does counting Yisrael result in a plague?
Moshav Zekenim citing the Rosh: It is only because they sinned (Chet ha'Egel). We find that Sha'ul counted Yisrael through sheep (Shmuel 1:15:4); he did not need Shekalim for a Kaparah! 3
Oznayim la'Torah: Directly
Why do people who are counted require a Kaparah?
Seforno: Because, bearing in mind that a decrease in numbers is the result of sin. 1 every census is automatically associated with sin. Consequently, every person who is counted must give a Kofer Nefesh in honor of Hashem, and Hashem in His mercy will atone for his sins. 2
Moshav Zekenim (citing the Rosh): It is only because they sinned by the Eigel that they needed to give specifically a half-Shekel. 3
As the Gemara states in Shabbos, 55a 'There is no death without sin'.
As the Torah concludes in Pasuk 15 (Seforno). See also Ba'al ha'Turim.
Like we find in Shmuel 2 24 - where a plague ensued when David counted Yisrael - preesumably because he counted them directly, and not via something else such as sheep (PF). Whereas on the other hand, the Pasuk in Shmuel 1 15:4 relates that Sha'ul counted Yisrael through sheep, and did not require Shekalim for a Kaparah.
If Hashem wanted Moshe to count Yisrael, why did He not command him directly?
Ramban: In fact, Hashem's instructions clearly indicated the obligation to count them, 1 and the reason that Hashem issued the command by inference was in order to extend the prohibition against counting Yisrael directly to all times. 2
Hadar Zekenim: Moshe was concerned that he will not be mentioned after he dies. Hashem told him, just like you erect Yisrael's heads now, so every year when Yisrael mention their Shekalim, I consider it as if you erect their heads.
Oznayim la'Torah: Because the half-Shekel that they were instructed to donate was to atone for the sin of the Golden Calf which had not yet taken place, 3 in which case to command them directly would have been premature. 4
Which Moshe did, as the Torah indicates (35:25) (Ramban).
Ramban: In fact, David ha'Melech (thinking that the prohibition was confined to this occasion only), missed this point and counted Yisrael, resulting in a plague.
And Hashem was only telling them in advance how they would have to atone after they had sinned
