"And Moshe assembled the entire community of the Children of Israel."
(Shmot 35:1)

What was Moshe doing?

Bnei Yisrael comprised of over 3 million people! What could be so important that Moshe had to gather that many people together?

Perhaps Moshe was trying to make a point. After all Bnei Yisrael had fallen from grace a bit with the construction of the Golden Calf. But Moshe had a trick up his sleeve. A great leader knows how to take advantage of every situation, even of a mistake. Really only three thousand people took part in the building of the golden calf, hardly a united front. However in this instance, Moshe was able to illustrate total unity. When it came to a Mitzvah, Moshe was able to assemble every single Jew, man, women, and child, there was absolute Achdut and complete unity.

Perhaps this idea can be seen in the pasuk qouted above, the very first pasuk of Parshat VaYakhel.

"And Moshe assembled the entire community of the Children of Israel and said to them: These are the things which G-d has commanded." Moshe gathered the people and said to them, "these are the things," meaning literally unity such as this, "this is what G-d has commanded," this is what G-d wants from his children.

Parshat Shekalim, the extra Torah reading which sometimes falls together with Parshat VaYakhel, essentially expresses the same idea.

No Mitzvah better asserts the idea of Achdut then giving a HALF Shekel. As Rav Shlomo Alkabez puts it, explaining why only half of a Shekel: "In giving a half Shekel each individual person remembers that in a state of disunity we are only a fragment of a nation. It is only in a sate of unity that we become whole, a complete nation. It is Parshat Shekalim that is read in the weeks prior to Shavuot, when we celebrate receiving the Torah. The great unifying force of the Torah can only be given to a unified nation."

Likewise in Parshat VaYakhel, before the Mishkan was to be completed, before the presence of G-d was to rest within the community of Israel, Moshe had to display that Bnei Yisrael were back on the right track, or better yet as Moshe saw it, had never left it to begin with.