The word "Israel" can be read as an acronym for "Yesh Shishim Ribo Otiot LaTorah", meaning: "There are six hundred thousand letters in the Torah". Therefore, Israel did not leave Egypt until there were six hundred thousand of them, in order for each soul to be "supported" by one letter in the Torah, as we have written in a number of places. When the voice is the voice of Jacob…then the hands are not the those of Esau…
We see that G‑d overlooks many serious sins but He does not overlook negligence in Torah study, as is written, "Why was the land lost? G‑d has said, 'Because of their forsaking My Torah.'" (Jeremiah 9:11-12) Even though they transgressed all of the sins, G‑d only accused them of negligence in Torah study. As our Sages have said regarding the verse "the voice is the voice of Jacob": (Gen. 27:22) when the voice is the voice of Jacob, that is, of Torah study, then the hands are not the those of Esau, that is, the forces of evil are powerless. But when the voice is not that of Jacob, then the hands are that of Esau and the forces of impurity dominate. Our Sages likewise explained that the reason that "Amalek came and fought with Israel at Refidim" (Ex. 17:18) was that their hands had slackened from the Torah. [This is derived from the word "Refidim" which has as its root the Hebrew word "rafa", meaning "slackening".]
Since the name "Israel" alludes to the fact that the number of letters in the Torah corresponds to the number of souls, it follows that when the Jewish People come to count their souls [take a census], the accuser comes and accuses them saying, "Master of the universe, didn't Israel only reach this size population in order to match the number of letters in the Torah which are hinted at in their name? And now they are negligent in [the Torah]!" This becomes the substance of the accusation. Israel…should awaken their fear of Heaven in order to repair their souls and spirits…
Furthermore, the word "negef", meaning "a scourge", has the same numerological value as 'Satan', the Angel of Destruction, short two. ["Negef" equals 133, while "Samael" equals 131.] The missing two allude to the two Torahs (Oral and Written). When Israel are lax in the two Torahs, two powers are added to those of the forces of evil, and it becomes "negef", a scourge, and afflicts them, G‑d forbid.
In fact, though, through the redemption money that Israel gives, the forces of evil have no power to rule over them, for charity is a protection against them, as is written, "Charity saves from death". (Proverbs 10:2)
All of G‑d's commandments are hints and allusions, to cause people to study G‑d's ways. As for why Israel was commanded to give a half-shekel, the word "shekel" has the same numerological value as "Nefesh", with half of it having the same value as the Hebrew word "yira", meaning "fear of Heaven" [including the word as a whole]. The other half has the same value as "Ruach". This comes to warn and inform Israel that they should awaken their fear of Heaven in order to repair their souls and spirits, for heavenly prosecution comes as a result of negligence in Torah study and the remedy is for them to accept upon themselves to study Torah with no interruptions. This follows from the principle that the form of repentance must match the sin, which means that besides for the redemption money that Israel gives, they must take upon themselves to study Torah, for the redemption money only atones for what is past, but from now on nothing can help them but actual Torah study.
[Petuchei Chotem, parashat Ki Tisa, as anthologized in Peninei Avir Ya'akov, p. 213;
Translated by M. Steinberger and E. Linas]