Rashi, in the name of Chazal, comments that three trumos, donations, were given by klal yisrael in the desert, one to supply the mishkan with animals for korbanos and two - one obligatory and one voluntary - for the building of the mishkan itself.   The obligatory donation, the machtzis hashekel,  was used for the construction of the adanim, the silver base of the mishkan.  The voluntary donation is the subject of this week's parsha , which specifies that it should be given by each person according to the desire of his heart.  What can we learn from this seemingly contradictory fundraising strategy and from the fact that the material for the adanim, which were the foundation of the mishkan, were funded only from the obligatory machtzis hashekel?

                      Rav Yerucham Olshin, shlita, Rosh Yeshiva of Bais Medrash Govoha, cites a medrash that states that the donations to the mishkan served to atone for the donations that klal yisrael had given willingly to build the egel hazahav, the golden calf.  Accordingly, to gain insight into the trumos of the mishkan, we would do well to investigate the sin of the egel hazahav.  What in fact was the sin of the egel?  The Bais Halevi in parshas Ki Sisa cites a medrash that b'nei yisrael glimpsed the chariot of Hashem at Har Sinai and wanted to replicate it as best they could.  The result of their misguided effort was the egel hazahav.  In other words, klal yisrael's original intention in making the egel was not to worship avodah zara (idolatry), but to have in their midst a physical object in which the shechinah, (the Divine presence) would rest.

                 This presents us with a paradox.  The donations for the egel and the trumos for the mishkan were given with virtually identical intentions -to create a resting place for the shechina.  Why, then, were the results so catastrophic in the first case, while the second time they led to the realization of our ultimate purpose: to have the shechina among us?  The answer, says the Bais Halevi, lies in the one critical factor that was present in the building of the mishkan but lacking in the making of the egel:  Divine commandment.  To be sure, there is nothing more precious than the performance of a mitzvah out of the desire of one's heart to draw near to Hashem.  However, there is another kind of mitzvah which is equally precious, and that is one that is performed out of a sense of obligation.  Each approach by itself is incomplete.  An action performed solely out of obligation lacks individual creativity and emotional connection.  Conversely,  action that is fueled purely by love and spiritual desire, without being grounded in a sense of duty, becomes but another form of egoism.    The ideal avoda is comprised of both elements.  It is an individual expression of a person's longing for connection to Hashem which is grounded in an uncompromising sense of duty and responsibility.

                                                               In forming the egel hazahav,  klal yisrael  acted purely out of love, but avoda based only on love is not enough; it must also be rooted in chiyuv (obligation).  Only when a foundation of chiyuv is established, can a person begin to use his or her own creativity to develop it further into avoda of spiritual longing and love.   This, Rav Olshin explains, is the key to the dual nature of the trumashamishkan.  Hashem desired that the mishkan be built with the materials that b'nei yisrael donated out of personal desire and love of Hashem.  However, this time would be different than the egel because the crucial factor of Divine command was present.  Klal yisrael gave of their possessions for the construction of the mishkan not just because they wanted to, but because they were commanded to do so, yet part of that offering was discretionary so that each person had the opportunity to invest creativity and individuality into the mitzvah.  The mishkan itself reflected this dichotomy.  Its foundation, the adanim, were made of the shekalim which each person was commanded to give in precisely the same amount.  Upon this foundation, the rest of the mishkan was built from donations freely given from the heart.