After the Golden Calf fiasco, Hashem tells Moshe to take a census and count Bnei Yisrael. Of course, Hashem does not count His children by lining them up and counting each one. Rather, Hashem informs Moshe that a half Shekel will be the standard method of counting. However, there is an obvious question: Why half a shekel and not a whole Shekel? After all, the money was going towards the building of the Mishkan. What was Hashem trying to tell us by commanding Moshe to take a census through a half Shekel collection?
Rabbi Reuven A. Stone gives a few answers to this question. One is that the half Shekel represents the half-day that Bnei Yisrael could not wait before resorting to the notorious idolatrous festivities of the Golden Calf. As we learn, Bnei Yisrael began counting the 40 days Moshe would be with Hashem a half day too early. When their 40th day came around without Moshe, they figured he had died up on the mountain, when in truth he was still alive. Since they just had to have a physical “vessel” for Hashem's Shechinah to rest in, they came up with the idea of a Golden Calf. Had they been a little more patient and waited another half day, they would never have sinned. Thus, Hashem is teaching us to have a little Savlanut (patience) with the use of a half Shekel.
Another reason for the half Shekel is that it is equivalent in value to a different coin of that time period worth six Gramsin. However, what is the significance of this value? The Golden Calf was “born” during the sixth hour of the day. Again, we see Hashem is giving us a tap on the wrist for worshipping idols. Similarly, a half Shekel is equivalent in value to ten Gerot. This is Hashem's way of saying, “You threw all ten of My Holy commandments back in My face with this abomination,” as there is a connection between the numbers six and ten.
Additionally, Yosef’s brothers sold him to merchants headed for Egypt. Some commentators believe that the half Shekel had nothing to do with the Golden Calf at all, but instead was the atonement for the sale of Yosef. However, how are the brothers related to the half Shekel? The brothers sold Yosef for ten silver Dinarim. Since ten Dinarim are worth five Shekalim, so without Yosef, each brother had one brother less and one more half Shekel. Now, Bnei Yisrael are making up for this by giving back a half Shekel.
However, other commentaries insist that the entire Golden Calf affair was, in part, Yosef's fault! Yosef became somewhat of an Egyptian celebrity after his brothers sold him to those merchants. In fact, they liked him so much that when he died, he was embalmed, one of the highest forms of Egyptian gratitude. We return to this week's Parsha, Ki Tisa, where Aharon is mixing the gold for the Golden Calf. How could a cow rise up out of Aharon's mixing pot? Yosef made his brothers promise to bring his bones out of Egypt when they left, so Moshe retrieved them from the watery grave they had been allotted by throwing a note into the river where he was buried. The note said “Arise, Ox” (Yosef's nickname and symbol was the ox,). The Eruv Rav, the Egyptian who followed Bnei Yisrael out of Egypt, seemed to enjoy causing trouble for the Jews and threw in that very note, causing the calf to be created. Thus, many commentators say that the whole incident with the Golden Calf can be accredited, in part, to Yosef.
Finally, the half shekel can teach Bnei Yisrael a positive lesson. This lesson is the lesson of “Kol Yisrael Areivim Zeh La Zeh,” that “All Jews are responsible for each other.” No single Jew could be part of the census by himself because it was taken in half Shekel measurements. Hashem did not want a whole Shekel to be the measurement because then a Jew could say, “I am part of the census as an individual.” Since the measurement was a half, and not a whole, every Jew had to acknowledge that he was part of a greater body than just his own. Only when one Jew took responsibility for another could they be counted as a whole.