“And the middle bar inside the boards, holding them together from end to end.” Inside the boards of the Tabernacle, there was a middle bar (bariach/בריח) that connected them all, making them one. (Note that bariach/ברח/middle board is an permutation of chaber/חבר/connect).
To connect two items, there must be a hollow in the middle, through which the middle bar can pass. This holds a deep secret: The Ba’al Shem Tov said that he can refute any logical Torah-learning argument. In other words, in every worldview, at every level and in every layer of reality, in any ‘world’ – there is always a point of vacuum – empty space, nothingness. (For example, the blind spot in our field of vision). It is specifically when we identify that point of nothingness that we can connect and weave all the dimensions and worlds together. Each of them has a lack that seeks to be filled.
On the other hand, a person who feels complete and believes that his worldview is impeccable, actually bears the greatest defect of all. Thus, the Ba’al Shem Tov, who strove to connect – emphasized that he could see the point of nothingness in everything, enabling him to join all layers of reality together.
The revelation of the Divine passes through the hollows inside the boards of the Tabernacle, permeating the entire world. This is a unique revelation, reaching from the loftiest of levels down to the lowest, weaving all of reality together with one thread. This is the positive hollow about which King David said, “And my heart is hollow inside me ”. I have a hollow in my heart. Through it, I connect to G-d.