The Torah presents the mitzvah of contributing to the mishkan in an unusual fashion. "V'yikchu Li teruma - Let them take for Me a portion (Artscroll translation). The Torah speaks of taking rather than giving even though ostensibly Bnai Yisroel are being called upon to give. Why?
The Kli Yakar offers a beautiful explanation. In the realm of Torah and mitzvos he who gives (in actuality) receives in return much more than he has given. For example, says the Kli Yakar, a teacher of Torah gives of his time, his wisdom, and, ultimately, himself. Nevertheless, Chazal teach us "umitalmidai yoser mikulam", I have learned more from my disciples than from my teachers. A teacher gives, but, in return, he receives even more than he has given. The Torah hints at this lesson by exhorting Bnai Yisroel to take a contribution to the mishkan. The contributors will be taking much more than they are giving.
This perspective on life has profound implications. For instance, at times we may feel burdened by requests - both institutional and personal - for tzedaka. "I'm busy now. Why must you bother me once again?" is a thought which, at times, flashes through our minds and engenders resentment within us towards our fellow Jew. But, in reality, the opportunity of tzedaka outweighs the demand. We are being approached for a finite sum, which, when given to a worthy cause, will yield eternal schar.
The Vilna Gaon comments that the word venasnu, and they shall give, is (as spelled in the original Hebrew) a palindrome. In light of the Kli yakar's insight, we can appreciate the significance of the palindrome. Giving is cyclical because one always receives in return.
The Torah "makes demands" on our time. (Time is not really ours, but that idea is best kept for some future occasion). When it's time to learn, to daven, to do chessed, etc. we silently wonder, "but when will I have time for myself?" When such plaintive questions arise, we would do well to review the lesson of "v'yikchu Li teruma".