The Tanaim asked this question and gave different answers.
Ben Zoma chose a pasuk that would undoubtedly be on many of our lists: Shema Yisrael.
Ben Nanas chose a pasuk that again, I am sure many of us would think of: V’ahavta l’reiacha kamocha.
The surprise is the view of Shimon ben Nanas, who chose the pasuk, “Es hakeves echad ta’aseh baboker…” That one is probably on no one’s list, yet the Midrash continues that this pasuk is the best choice. The Midrash brings proof from another pasuk in our our parsha: “K’chol asher ani mareh oscha es tavnis hamishkan v’es tavni kol keilav v’kein ta’asu.”
The pasuk of “Es hakeves ha’echad…” refers to the daily korban tamid offering. How does this idea encapsulate the entire Torah? And what does the pasuk in our parsha that talks about the construction of the Mishkan have to do with it?
Ksav Sofer explains as follows:
Shema Yisrael is not only a personal statement of kabbalas ol, acceptance of the yoke of Torah and mitzvos, but is also a call to one’s fellow Jew. When we say (as commonly translated), “Hear Israel…,” we are addressing others and declaring to them that G-d is one. The essence of Judaism is not just belief in G-d, but also encompasses concern for the spiritual welfare of our brothers and sisters.
Ben Nanes went a step further. It’s not just the spiritual welfare of others which we must be concerned for, but also their physical needs as well. “V’ahavta l’reiacha kamocha” means whatever I would do for myself, I would do for my fellow Jew as well.
Ben Zoma and Ben Nanes both recognize that a man cannot live for himself, but in both of their worlds there is still a “Me” that reaches out to a “You.” Shimon ben Nanes went yet one step further. “Es ha’keves ha’echad ta’aseh baboker,” we are commanded “ta’aseh,” in the singular, to offer a korban tamid. There is not a “Me” or a “You” doing the offering, but rather there is a new collective entity called the community of Klal Yisrael, in the singular.
The truth is that the Mishkan could have been built with the donations of a few mega-wealthy donors. It did not require the participation of the community as a whole. Nonetheless, the Torah invited everyone who wanted to contribute to do so. “V’kein ta’asu” is not just a command that applies to the immediate mitzvah of building the Mishkan, as the “vav” in “v’kein” would be extra were that the case (see Rashi, Ramban). Rather, it is a command that extends to all mitzvos. Just as the community as a whole involved itself in the building of the Mishkan, so too, all mitzvos are strengthened and become more meaningful when the community as a whole participates in their performance.