“…And you shall place into the ark the testimony, which I will give you….” – Shemos 25:16

וְנָתַתָּ אֶל הָאָרֹן אֵת הָעֵדֻת אֲשֶׁר אֶתֵּן אֵלֶיךָ – שמות כה, טז

The Talmud (Berachos 8b) teaches that contained in the Aron were the unbroken second Luchos, as well as the broken remnants of the first Luchos. These contents reflect three phases experienced by Bnei Yisrael, signifying that building the Mishkan, (whose primary function is to serve as a home for the Aron, see Ramban, Introduction to Parshas Terumah,) is a task associated with every Jew, regardless of his current spiritual status.

The first Luchos were given to Moshe immediately following the G-dly revelation at Sinai, before Bnei Yisrael sinned and worshipped the Golden Calf. At that point, Bnei Yisrael were spiritually perfect, having been cleansed at the Giving of the Torah from any spiritual filth (see Talmud, Shabbos 146a). The remnants of the first Luchos thus represent the Jew in his purest and most elevated state.

The second Luchos were given on Yom Kippur, after G-d pardoned Bnei Yisrael for the sin of the Golden Calf. These Luchos represent the Baal Teshuva, a person who may have strayed from the Torah in the past but has since corrected and repented for his wrongdoings.

Finally, there is the third Jew who is represented in the Holy Aron: the Jew who has transgressed the Torah but has not yet mended his ways. The first Luchos – the Luchos of flawlessness, can no longer represent him, but the second Luchos, the Luchos of repentance, don’t represent him either. His is, however, represented by the fact that the first Luchos are found in the Aron in broken form. His sorry spiritual state notwithstanding, this Jew too can and must take part in building the Mishkan.

—Likkutei Sichos, vol. 6, pp. 156-157