ועשית את הקרשים למשכן עצי שטים עמדים You shall make the planks of the Mishkan of acacia wood standing erect
The Gemara in Yoma (72b) explains that the posuk means that the planks will be standing forever. Rashi’s comment on the Gemara explains that, therefore, we should never stop hoping for the return of these planks. The Ber Yosef (Rabbi Yosef Salant) is bothered by this Rashi: we all pray for the Beis Hamikdash to be built speedily in our days, but who prays for the return of these planks of wood? Furthermore, if the message of the Gemara is that the Mishkan will not be destroyed, why use the planks to represent this concept?
The Ber Yosef answers by quoting the Tanna D’bei Eliyahu which explains that, unlike the Beis Hamikdash, the Mishkan was not destroyed; rather, it was hidden by Hashem. This is because the Mishkan was built through the eagerness of the people to give to the communal cause. Since it was done with this willingness, Hashem did not want to destroy it. When the right time arrives, Hashem will bring it out and rest His divine presence there. For this reason, the Ber Yosef explains that we should have hope not just for the building of the Beis Hamikdash, but for the return of the Mishkan as well. This is the promise to which the pasuk is alluding: due to the great dedication of the Jewish people, the Mishkan will never be destroyed and Hashem will always rest His divine presence there.
This still doesn’t answer the question of why the planks of wood would convey the promise, as the promise is about the entire Mishkan. The Ber Yosef answers this question by examining the background of how the Jewish people obtained this wood. When Yaakov went down to Egypt, he stopped at Beer Sheva. The Medrash clarifies that he went there to cut down the trees that Avraham had planted. He brought these trees down to Egypt with him, and instructed his children and grandchildren to take these trees with them when they would leave Egypt in order to be able to build the Mishkan from them. Imagine the self-sacrifice of Yaakov taking the time to be concerned with bringing trees – at the very moment he was about to be reunited with his son. This is the son whom he had not seen in 22 years, the son whom he had yearned to see and for whom he had not been comforted since he had last seen him. For Yaakov to stop on his way to make sure that these trees would be available for the Jewish people when they left Egypt took an unbelievable amount of self-sacrifice! This was the reason Hashem did not want to destroy the Mishkan. The planks of wood were the greatest representation of the willingness to sacrifice anything for the opportunity to help build the Mishkan. For this reason, Hashem promised never to destroy the Mishkan and always to rest His divine presence there.
We should learn from this the importance of being willing to sacrifice our own personal desires in order to benefit the entire Jewish people. Through our dedication and self-sacrifice for the community, we will hopefully once again be able to bring back the Mishkan in our days.