Every individual completes the collective Mishkan

מאת כל איש כו' תקחו את תרומתי.

"From every man… you shall take My terumah (offering)" (Shemos 25:2).

The Sefas Emes opens on the verse commanding that the contribution for the Mishkan be taken "from every man," and he focuses on the role of the individual.

פי' שגם הכלל צריך לפרט.

This means that even the collective whole needs the individual.

"From every man" teaches that the klal (the totality of Bnei Yisrael) is not complete without each prat (individual); the whole depends on the contribution of each single person.

וזאת צריך כ"א לידע כי מעשיו נוגעים לכללות בנ"י.

And this every person must know — that his deeds bear upon the entirety of Bnei Yisrael.

Each individual must internalize that his own actions are not private but affect the whole Jewish people; no one's avodah is insignificant to the klal.

ואיתא באלשיך ע"פ ועשו לי מקדש ושכנתי בתוכם. בתוכו לא נאמר. רק שע"י מעשה המקדש אשכון בתוכם של בנ"י ממש ע"ש:

And it is brought in the Alshich on the verse "And they shall make Me a Sanctuary, and I will dwell among them" — it does not say "within it," but rather that through the making of the Mikdash, I will dwell within Bnei Yisrael themselves; see there.

Citing the Alshich, he notes the precise wording: Hashem promises to dwell "among them" — within the people — not "within it," the building. The purpose of the Mishkan is to draw the Shechinah into the hearts of Bnei Yisrael themselves, which can happen only when each individual contributes his part.

Summary: "From every man you shall take My terumah" teaches that the klal needs each prat — every individual must know that his deeds affect all of Bnei Yisrael. As the Alshich notes, "I will dwell among them," not "within it": the Mishkan's true purpose is for the Shechinah to rest within the people themselves, which depends on the contribution of each and every Jew.