"Eleh pekudei hamishkan, mishkan ha'edus"  ("These are the reckonings of the Mishkan, the Mishkan of Testimony.")   Rashi, in the name of the medrash, explains that since the Mishkan was graced with the presence of the Shechina, it bore witness that Hashem had forgiven Bnei Yisrael for the sin of the egel hazahav (Golden Calf).  The mefarshim (commentators) ask: Wasn't the fact that Hashem gave us a second pair of luchos sufficient evidence of forgiveness?  What, then, was purpose of the testimony of the Mishkan?

Chazal teach that there was an essential difference between the first luchos and the second.  While the stones of the first luchos were supplied by Hashem, the stones of the second were supplied by Moshe, as per Hashem's command.   Rav Dessler explains in the name of the Radvaz that the stones of the luchos represented the collective heart of Klal Yisrael, and the difference between the stones of the first luchos and of the second reflected the different spiritual states of this heart when receiving the two pairs of luchos.  At Matan Torah, when the first luchos were given, Bnei Yisrael were so completely devoted to the Torah that our hearts were purified of any wayward tendencies, and the Yetzer Hara lost all power over us.  Yisrael's heart at this level was symbolized by the stones supplied by Hashem Himself -heavenly and perfect.  Forty days later, though, as a result of the sin of the egel hazahav,  that lofty spiritual state was diminished.  Although Hashem gave the second pair of luchos, signifying that the sin was forgiven, the Jewish people no longer had the pure heart symbolized by the heavenly stones of the first luchos.  Instead, our hearts were much the same as they are now -flawed, and prone at times to choose falsehood over truth.  The heart in this imperfect state was represented by stones that were supplied by a mere mortal.

With the state of our hearts, our mission as a people changed, as well.  Instead of experiencing permanent closeness to Hashem, we must now struggle with our baser inclinations in the constant attempt to subjugate our hearts to Hashem's will.  After the chet ha'egel, a single question burned in the minds of Klal Yisrael: Are we forever incapable of regaining our former spiritual glory?  Is the lofty state we once achieved now just a distant memory, or do we still have the power of realizing it again?  Receiving the second luchos gave Bnei Yisrael reassurance that had been given reprieve, but it did not allay their anxiety about their capacity to realize their highest potential.  This is why the testimony of the Mishkan was necessary.

In his commentary on Parshas Teruma, the Ramban writes as follows: "The secret of the Mishkan is that the glory that had resided on Har Sinai would rest upon it in a hidden fashion...and the glory that had appeared to them on Har Sinai was constantly with Yisrael in the Mishkan."  In other words, the revelation on Har Sinai would now be relived, on a permanent basis, within the Mishkan.

It is in this sense that the Mishkan bore witness not only that the sin of the egel was forgiven, but that its corrosive effects on the spirit of the Jewish people could be reversed. True, the spiritual level of the Jewish people was rendered fundamentally lower by the sin of the egel than it was at Matan Torah, and that makes the goal of hiskarvus to Hashem more difficult.  However, the sublime state we once achieved at Har Sinai is not just another event in our national history.  We may still look to that lofty state as an inspiration and a lifelong goal, because in every generation we have the ability to regain it. It is still possible, through a lifetime of self-perfection, to elevate ourselves to the lofty heights and state of spiritual purity we once experienced.