Purification precedes the renewed choosing

חז"ל הקדימו פרה לחודש.

Chazal placed [the reading of] Parah before [the reading of] HaChodesh.

In the cycle of special Torah readings before Pesach, Parshas Parah is read before Parshas HaChodesh; the Sefas Emes explains the spiritual order this reflects.

כי בחודש ניסן מתעורר בחירה חדשה בכל שנה שהקב"ה בוחר בעמו ישראל.

For in the month of Nissan a new bechirah (choosing) is awakened every year, in which the Holy One, blessed be He, chooses His people Yisrael.

Each year in Nissan, Hashem's choice of Bnei Yisrael is renewed afresh, just as it first occurred at the Exodus.

ומתחילה ביציאת מצרים החודש הזה לכם.

And originally, at Yetzias Mitzrayim, "this month is for you" (Shemos 12:2).

This annual renewal traces back to the first Nissan, when Hashem gave Bnei Yisrael the mitzvah of "hachodesh hazeh lachem," marking His choice of them.

ואח"כ אחר שנתקן החטא נתקרבו ג"כ אליו בחודש ניסן כמ"ש ביום השמיני.

And afterward, once the cheit was rectified, they were also brought close to Him in the month of Nissan, as it is written "on the eighth day" [of the Mishkan's inauguration].

After the sin of the Golden Calf was repaired, Bnei Yisrael drew near to Hashem again in Nissan, at the dedication of the Mishkan on the eighth day.

ויקרבו כל העדה כו'.

"And the whole congregation drew near [and stood before Hashem]" (Vayikra 9:5).

This pasuk describes the people approaching Hashem at the Mishkan's inauguration — the aspect of kerivah, drawing close.

וב' הבחי' אלו בחירה וקריבה הם תמיד לבנ"י.

And these two aspects — bechirah (being chosen) and kerivah (drawing close) — are always [present] for Bnei Yisrael.

Two ongoing dynamics define Bnei Yisrael's bond with Hashem: His choosing them, and their drawing near to Him.

וע"ז אומרים אתה בחרתנו כו' וקרבתנו כו' לעבודתך.

And about this we say: "You have chosen us… and brought us close… to Your service."

The Yom Tov tefillah captures both: "atah vechartanu" (You chose us) and "vekeiravtanu" (You brought us close to Your avodah).

ועתה אין יכולין לבוא לבחי' בחירה רק בהקדמת בחי' קריבה ע"י התשובה.

And now we cannot arrive at the aspect of bechirah except by first preceding it with the aspect of kerivah, through teshuvah.

In our era, we cannot simply receive Hashem's renewed choice; we must first draw ourselves close to Him through teshuvah, which then makes us fit to be chosen.

וזה הקדמת פרה לחודש.

And this is [the reason for] placing Parah before HaChodesh.

Parah, which deals with purification, represents the kerivah of teshuvah that must precede the bechirah of HaChodesh.

דכתיב כאשר עשה כו' צוה כו' לעשות דרשו חז"ל לעשות זו מעשה פרה.

For it is written "as he did… [Hashem] commanded… to do" (Vayikra 8:34), and Chazal expounded: "to do" — this refers to the maaseh parah (the rite of the red heifer).

Chazal read the phrase "laasos" as alluding to the maaseh parah, the purification rite, connecting it to this season of renewal.

ויתכן שהוא רמז כי בכל שנה קודם ניסן מתקיים עשי' זו ויורד משמים טהרה לנפשות בנ"י המצפים לטהרה.

And it may be that this is a hint that every year, before Nissan, this "doing" is fulfilled, and taharah (purity) descends from Heaven upon the souls of Bnei Yisrael who yearn for taharah.

The Sefas Emes suggests that even without the actual red heifer, every year before Nissan a heavenly purification is granted to those who long for it, fulfilling the "doing" of Parah in a spiritual way.

ולא לחנם קבעו חז"ל לקרות פ' פרה בשבת זה רק שיכולין עתה לזכות לטהרה:

And not for naught did Chazal establish the reading of Parshas Parah on this Shabbos — rather, [it is] because now we are able to merit taharah.

Chazal's placement of the Parah reading at this time is purposeful: it is a season when Bnei Yisrael can actually attain spiritual purity in preparation for the renewed bechirah of Nissan.

Summary: Each Nissan, Hashem renews His choice of Bnei Yisrael (bechirah), just as at the Exodus, and they in turn draw close to Him (kerivah), as at the Mishkan's inauguration. But in our time we cannot reach the renewed bechirah without first achieving kerivah through teshuvah — and this is why Chazal placed Parah, the parsha of purification, before HaChodesh. Reading Parshas Parah at this season is no accident: every year before Nissan a heavenly taharah descends upon the souls of Bnei Yisrael who yearn for it, enabling them to merit purity and be ready for Hashem's renewed choosing.