Speak unto the children of Israel, that they take for Me an offering; of every man whose heart makes him willing you shall take My offering.
Exodus Rabbah Chapter 33
At the time that the Holy One blessed be He told Moses about all the tasks associated with the (building of the) tabernacle, Moses said before him; "Master of the universe will the Israelites be able to do this?" The Holy One blessed be He said to him "Even (a single) one of the Israelites could do it." As it is written "of every man whose heart is willing."
This midrash makes great meaning out of a small grammatical point. It seems that the midrash is responding to the peculiar shift from speaking of the Israelites as giving gifts collectively to emphasizing the individual gift. This was to be a monumental collective effort, and the midrash imagines Moses being concerned about getting the level of cooperation needed to make it happen. Given what he already knows about the difficult nature of this group, we can understand Moses's worry. Our midrash imagines God reassuring Moses that this is a task that can be achieved by even a single Israelite.
That is why God asks that the gifts be from the willing. God seems not to be seeking out the work alone, but more the voluntary offering. I find this to be incredibly encouraging. It seems that often in life we could ask, "What's the point of trying so hard when no one else is?" We could apply this to our environmental efforts, our religious strivings, or any tough choices we make in the face of a culture that works against our efforts. We feel that even if we give it our all, we alone can never save the planet, or create a strong Jewish community. Our midrash comes to tell us that God is concerned even with our small individual gifts, and that those are as dear as the great collective efforts.
The incredible thing, of course, is that the Mishkan does get built. That is the best message of all. You see, when individuals started giving to the Mishkan, an amazing thing happened. They inspired others to do so as well. That is the real power of one. Each of us may not be able to tip the scales on our own, but our efforts can inspire others to follow and to make the change we never could have made on our own.