Our Parsha begins with an appeal for funds on behalf of the Mishkan, as the Posuk states "ויקחו לי תרומה," and they shall take for me a donation (שמות כ"ה:ב'). Virtually all Darshanim are troubled by the selection of the word ויקחו, and they shall take, when the more appropriate phrase would be ויתנו לי תרומה, and they shall give a donation for me. In reality, the Torah itself provides the answer to the question, concluding the Posuk by saying "מאת כל איש אשר ידבנו לבו תקחו את תרומתי", take a donation only from those inclined to give. There is no כפייה, coersion, to give for the construction of the Mishkan.
The question, however, arises as to why this Tzedakah is different from all others. Every Jew, for example, was required to participate in the contribution of the מחצית השקל, the half-Shekel. In general, we understand that Tzedakah is not really an act of Chessed, but a sacred obligation incumbent upon all Jews. One is required not only to respond to the needs of individuals faced with economic problems, but also to participate in the building of community institutions, such as Mikvaos, Batei Midrash, Shuls, and Yeshivos. The Halacha states emphatically "כופין בני העיר", the Beis Din has the right to compel members of the community to participate in such projects. Why, then, would contributing toward constructing the Mishkan be totally voluntary?
After concluding the building of the Beis HaMikdash, Shlomo HaMelech stated "הנה השמים ושמי השמים לא יכלכלוך אף כי הבית הזה אשר בניתי" (מלכים א'ח;כ"ז), the heavens themselves can't contain Hashem, certainly this Beis HaMikdash can not really contain Him. In reality, the Mishkan and Mikdash are not really for Hashem's sake, but for man's. Outside the Beis HaMikdash, one can experience only a reflection of His spirit. Through comprehending the beauty of nature, one should be moved to sing the praises of Hashem; when one sees the heavens, the שמי השמים, and the other wonders of nature, one recites הללוקה. But one does not see Hashem Himself. During fleeting moments of history, such as Yetzias Mitzrayim, Kerias Yam Suf or Mattan Torah, we have indeed been זוכה to that which we call גילוי שכינה, Divine Revelation. However, in the Mikdash, the אוהל מועד, the meeting place, one always enjoys the opportunity to meet Hashem's Shechinah.
Hashem created the world to reside in it and not to be afar in a transcendental world. Unfortunately, man's sins and digressions often keep Hashem at a distance. The Mikdash represents a unique opportunity to restore a relationship, and for this reason there is no כפייה, no coersion. If man does not cherish the opportunity to have Hashem reside within his midst, we don't force him, and Hashem does not need the Mishkan. As such, the appeal is directed only to "כל איש אשר ידבנו לבו, " and from such people only "תקחו את תרומתי."