The Torah portion of Ki Tisa contains the commandment of the half-shekel, symbolic of the mitzva of tzedaka (charity). There are several ways in which an individual can give tzedaka. The first is when a person is kindly and giving by nature, or when he understands intellectually the need to help his fellow man. However, this is considered the lowest level of giving tzedaka.
A higher level is when a person gives tzedaka because G-d has commanded him to do so. In this instance the incentive is not personal, but stems from the desire to obey G-d's will. A mitzva is absolute and not subject to intellectual or emotional considerations. Thus, when a person gives tzedaka out of a sense of obedience, his action is imbued with greater power. Yet even here, there can be mixed personal motivations, such as the fear of punishment or the desire to receive a reward (material or spiritual) in this world or the next.
Above these two levels is the giving of tzedaka "without any intent of receiving a reward." In this instance, the mitzva (commandment) is fulfilled out of pure and simple obedience to G-d, without any thought of recompense. The person wants to fulfill G-d's will, and enjoys doing so.
The mitzva of the half-shekel, however, represents the very highest category of giving tzedaka. On the verse in this week's portion, "This shall they give...a half-shekel...an offering to G-d" (the commandment for every Jew to give the half-shekel), the Jerusalem Talmud comments: "G-d removed a coin of fire from under the Throne of Glory and showed it to Moses, saying, 'This shall they give.' " Indeed, the "secret" of the half-shekel is related to the idea of "a coin of fire."
The nature of fire is always to ascend upward; it has no "weight" or fixed, definable form. Similarly, the optimal way to give tzedaka is with a fiery "flame" and enthusiasm, without any personal considerations or motives. In this scenario, the Jew just naturally desires to fulfill G-d's will, and doesn't even look for other reasons or justifications.
Nonetheless, it is significant that G-d showed Moses a "coin of fire," rather than just a flame. When a person gives tzedaka (or does any other mitzva, for that matter), theoretical abstracts are not enough. The point is to bring down that fiery enthusiasm to a physical level where it can actually help someone down here, and be expresed in the realm of physical and concrete action.
When the mitzva of tzedaka is done in this manner, a Jew will give unconditionally, without waiting for specific times and without even waiting to be asked. His inner "fire" will prompt him to seek out those in need, and he will happily do so repeatedly, again and again.
