The Half Shekel
“God showed Moshe a coin of fire weighing half a shekel, and He said, ‘They should give one like this’” (Rashi v. 13).
Fire differs from all other elements on this earth, in that it strives upward, reaching ever higher, dancing, flickering, until finally it frees itself of its chains when the wick burns out and it unites with its source. Fire is the paradigm of self-effacement, having no distinct shape or form of its own.
A coin, however, is hewed from the depths of the earth, the lowest of the four elements that constitute the makeup of this world. The antithesis of fire, the coin falls ever downward, clearly defined in its shape and form. Fire represents the transcendence of the spiritual; a coin represents the crassness of the physical.
It was not despite the sharp contrast between them, but specifically because of it, that God showed Moshe a coin of fire. God taught Moshe that the coarse and the unrefined is not necessarily the antithesis of the most holy and pure. The physical does not repel the spiritual, rather they can work in harmony, until they reach complete fusion, absolute unity, as represented by a coin made of fire.
On a practical level, God taught Moshe that even coarse human beings who are naturally driven by selfish motives, self-love being their basic instinct, can also serve the Divine with the most noble of services, as represented by the complete selflessness of fire.
(Based on Sichas Shabbos Parshas Ki Sisa 5749)