Preparation purifies the mitzvah

איתא בגמ' אמר ר"ל גלוי וידוע לפני המקום שעתיד המן לשקול כו' והקדים שקלי ישראל.

It is taught in the Gemara: Reish Lakish said, it was revealed and known before the Omnipresent that Haman would in the future weigh out shekalim, and therefore He caused the shekalim of Yisrael to precede his (Megillah 13b).

Because Hashem foresaw that Haman would pay silver to destroy the Jews, He arranged that the mitzvah of the machatzis ha-shekel would come first and counter it.

והיינו דתנן באחד באדר משמיעין על השקלים והכלאים.

And this is what we learned in the Mishnah: on the first of Adar we announce concerning the shekalim and the kilayim (forbidden mixtures) (Shekalim 1:1).

The Mishnah pairs the announcement of the shekel-collection with the warning about kilayim, and the Sefas Emes will explain why these two belong together at the start of Adar.

והענין הוא כי ראשיתן של בני ישראל בניסן חודש האביב כמ"ש ראשית תבואתו.

The matter is this: the beginning of Bnei Yisrael is in Nissan, the month of spring, as it is written, "the first of His harvest" (Yirmiyahu 2:3).

The true "beginning" and ripening of Yisrael belongs to Nissan, when the grain ripens — Yisrael are Hashem's first and choicest produce.

אבל עמלק ראשית גוים הוא באדר שבו מתחיל הקש לצמוח כמ"ש ובית עשו לקש והוא שכתוב יכין רשע וצדיק ילבש כי הקשים מכינים מקום להתבואה הבאה אח"כ.

But Amalek, "the first of the nations" (Bamidbar 24:20), is in Adar, when the straw (kash) begins to grow, as it is written, "and the house of Esav shall be straw" (Ovadiah 1:18); and this is the meaning of "the wicked one prepares but the righteous one will wear it" (Iyov 27:17) — for the stalks of straw prepare a place for the grain that comes afterward.

Amalek/Esav is like the straw that sprouts before the grain. The kelipah (husk) appears first only to make room for the holy "grain" of Yisrael that ripens after it; the rasha's effort ultimately serves the tzaddik.

וכן הוא לעולם הקליפה קודם לפרי.

And so it always is — the kelipah (husk) precedes the fruit.

In the natural and spiritual order alike, the outer shell forms before the inner fruit it protects.

אבל בני ישראל צריכין להקדים עצות לבטל הקליפה והפסולת.

But Bnei Yisrael must take measures in advance to nullify the kelipah and the waste matter.

Yisrael are not passive before the husk; they must prepare strategies to clear away the shell and the dross before the fruit can emerge cleanly.

והוא בחינת הכנה של המצוה.

And this is the aspect of the preparation for the mitzvah.

That advance clearing-away is the hachanah (preparation) that precedes and enables the mitzvah itself.

שהרי התרומה הי' בניסן.

For the actual terumah (the shekel-collection) was in Nissan.

The shekalim were truly used beginning in Nissan, the month of Yisrael's ripening.

ומ"מ באדר משמיעין שהוא הכנה.

And nevertheless, in Adar we announce — for that is the preparation.

The announcement a month earlier, in Adar, is the preparatory stage that readies and purifies the coming mitzvah.

ובכח זה מתברר התערובות ומסירין הפסולת.

And through this power the mixture is clarified and the waste is removed.

The Adar preparation sifts out the admixture of evil so that only the pure remains for the mitzvah.

וכן הוא בכל מצוה.

And so it is with every mitzvah.

This pattern of preparation-then-fruit applies to the performance of any mitzvah.

כפי הכנה הטובה נעשה המצוה בלי פסולת.

According to the good preparation, the mitzvah is performed without waste.

The quality of one's hachanah determines how cleanly and purely the mitzvah itself is fulfilled, free of dross.

והיינו דתנן על השקלים ועל הכלאים:

And this is what we learned: "concerning the shekalim and concerning the kilayim."

Both announcements are about clearing away improper admixture — the kilayim warning to separate forbidden mixtures, and the shekalim to prepare and purify Yisrael for the coming avodah.

Summary: Hashem arranged that the machatzis ha-shekel would precede Haman's silver. Yisrael's true ripening is in Nissan, while Amalek and the kelipah, like straw, sprout first in Adar only to make room for the holy fruit. Therefore Yisrael must take preparatory measures in Adar to clear away the husk and dross; this hachanah purifies the coming mitzvah. The Mishnah pairs shekalim and kilayim because both concern removing improper admixture so the mitzvah emerges pure.