The Bais Hamikdash was the root of Achdus, as the Posuk says, “כעיר שחברה לה יחדיו”, and the Bais Hamikdash encompassed all of Klal Yisroel, and was the root of the Creation, for the אבן שתיה was there; and the entire world was nourished from there. The people of the Dor Haflagah wanted to build a city and a tower, as they were trying to imitate the Kedusha – but instead have Tumah. The city corresponded to the holy city of Yerushalayim, and the tower corresponded to the Bais Hamikdash, for there was the root of the Achdus of Klal Yisroel. The Posuk says, “ועתה” and the Midrash says that this is a Loshon of Teshuva – that Hakodosh Boruch Hu opened the gates of Teshuva and gave them an opportunity to do Teshuva. That which Hakodosh Boruch Hu gave them the opportunity to do Teshuva is explained by the Zohar Hakodosh, that the reason for this opportunity was from the Koach of their Achdus. The Koach of the Achdus protected them from evil, from having what happened to the Dor Hamabul happen to them. The Zohar concludes with a Kal V’chomer, that if there is Achdus amongst the wicked, which really has no connection to true Achdus, and it protected the Dor Haflagah that they should not be obliterated, then certainly the Achdus of Klal Yisroel, which is true Achdus, as they connect it to Hakodosh Boruch Hu, that it will protect them and ensure no harm come upon them. Although the Posuk does not say it directly, when the Torah says, “וירד ד' לראות” – Hashem descended – that means that the Shechina came down to this world – a time when it is easier to do Teshuva. In truth, it was a test to see what their Achdus was all about. When the Shechina came down, were they going to rise to the Shechina, and seek to attach themselves to it, and in that case, it would be known that it was true Achdus. However, the response to this, “לא יבצר מהם כל אשר יזמו לעשות” – that no, they were not going to attach themselves to it, and thus their Achdus was not going to be a lasting one.
