The pasuk says, "And you shall make the planks from shitim wood" (Terumah 26:15). Rashi comments that the Torah does not say "you shall make planks," but rather "you shall make the planks" because the beams of the Mishkan were not made from any ordinary wood; they were made from the trees that Yaakov Avinu planted in Mitzrayim. Chazal elaborate further (Midrash Rabbah, Vayigash 94:4) that Yaakov Avinu stopped in Be'er Sheva on his way down to Mitzrayim to take trees from Avraham Avinu's "eshel" so that he could replant them in Mitzrayim and later Klal Yisrael would be able to use wood from those trees for the planks of the Mishkan, and specifically for the middle beam, the briach ha'tichon, which kept all the planks together (see Targum Yonason, Terumah 26:28, for a different version of this Midrash).
Why did Yaakov Avinu want the middle beam to be made from Avraham Avinu's eshel? Chazal (Sotah 10a) cite two opinions as to whether the eshel was an orchard or an inn, but either way it was a place where Avraham Avinu would invite guests to eat and rest. This was where Avraham Avinu, the pillar of chessed, engaged in acts of kindness and generosity. It would seem that Yaakov Avinu wanted Klal Yisrael to use this eshel in building the Mishkan in order to infuse the middah of chessed in the very planks of the Mishkan, and especially in the briach ha'tichon, the middle beam, which kept the Mishkan together.
Why did the Mishkan require a foundation of chessed? The Ramban writes in his introduction to Parshas Terumah that the Mishkan was intended to be like Har Sinai; the goal was that the Shechina which rested on Har Sinai should dwell in the Mishkan. Before kabbolas haTorah, the pasuk says, "And (Bnei) Yisrael camped there (Yisro 19:2)" Chazal comment that the word "camped" - vayichan - is written in singular form to teach that Klal Yisrael camped before ma'amad Har Sinai "as one man with one heart" (see Rashi there).
In order for Klal Yisrael to experience the Divine Revelation of ma'amad har Sinai, they first had to unite as one because the Shechina dwells among Klal Yisrael in its fullest sense only when they are united. This is the kind of perspective that Yaakov Avinu wished to instill in the Mishkan by using wood from Avraham Avinu's eshel. When Klal Yisrael would see the planks that symbolize the values of kindness and sensitivity, they would draw closer together and that would cause the Shechina to dwell in the Mishkan.
This idea is also highlighted by the keruvim that were placed on top of the aron. The pasuk says, "And the keruvim should be with their wings spread upward...with their faces toward each other (uf'neihem ish el achiv)...It is there that I will set My meetings with you and I shall speak with you...from between the two keruvim" (Terumah 25:20,22). Hashem spoke with Moshe and rested his Shechina so to speak between the two keruvim. Why specifically in that place?
The Kli Yakar (Kedoshim 19:18) suggests that the wings of the keruvim were spread upward to symbolize mitzvos bein adam l'Makom, while their faces were turned toward each other to symbolize mitzvos bein adam l'chaveiro. Both types of mitzvos must be fulfilled properly in order to achieve perfection - shleimus. That is why, says the Kli Yakar, the ten commandments are split equally; the first five are bein adam l'Makom, while the second five are bein adam l'chaveiro. This shows that the two types of mitzvos are of equal importance.
When a prospective convert approached Hillel and asked him to teach him all of Torah on one foot, Hillel responded, "What is hateful to you, do not do to your friend. (Shabbos 31a)" In other words, he told him, "You should love your friend as yourself." The Kli Yakar explains that by asking to be taught all of Torah on one foot, the prospective convert was not playing games. He was really asking, "What is the one foundational principle of the Torah, on which everything else stands?" Hillel responded with the pasuk, "You should love your friend as yourself; I am Hashem. (Kedoshim 19:18)" This pasuk encapsulates the two types of mitzvos that encompass the entire Torah. "V'ahavta l'rei'acha kamocha" is the basis for mitzvos bein adam l'chaveiro, while "ani Hashem" underscores the importance of mitzvos bein adam l'Makom.
The positioning of the wings and faces of the keruvim on top of the aron reflected this duality of mitzvos as well. Perhaps that is why Hashem specifically chose that space between the keruvim as his meeting place with Moshe, to emphasize that his Shechina will rest on the Mishkan only if Klal Yisrael maintains a proper balance between mitzvos bein adam l'Makom and mitzvos bein adam l'chaveiro. It is not enough for them to focus their attention on serving Hashem through the avodah of korbanos and tefillah, with their arms outstretched to the heavens. Their faces must also be "ish el achiv" - acting toward each other with compassion and sensitivity.
The more we internalize the dual message of the keruvim, the more we can hope to merit the protection and the blessing of the Shechina.