Renewal of creation through the new month

החודש הזה לכם.

"This month shall be for you." (Shemos 12:2)

Hashem gives Bnei Yisrael the first mitzvah of sanctifying the new moon. The Sefas Emes reads "for you" as Hashem handing over a power that now belongs to Bnei Yisrael — the power of renewal.

הוא כח התחדשות שהבורא ית' מחדש בכל יום מעשה בראשית בכח התורה וקודם יציאת מצרים לא היו יכולין בנ"י לקבל זה התחדשות דאין כל חדש תחת השמש:

This is the power of renewal (hischadshus), by which the Creator, may He be blessed, renews the work of creation every day through the power of the Torah; and before yetzias Mitzrayim Bnei Yisrael could not receive this renewal, for "there is nothing new under the sun." (Koheles 1:9)

The mitzvah of the new month embodies hischadshus (constant renewal): Hashem re-creates the world each day through the Torah. So long as Bnei Yisrael were trapped in Mitzrayim — inside the closed natural order where "there is nothing new under the sun" — they could not tap into this renewal. The Exodus opened them to a reality above unchanging nature, where every moment can be made new.

Summary: The first mitzvah given to Bnei Yisrael, sanctifying the new month, grants them the power of hischadshus — the ongoing daily renewal of creation that flows through the Torah. Only after leaving Mitzrayim, and rising above the fixed natural world of "nothing new under the sun," could they receive this gift of perpetual renewal.