On the verse, “Who is she who appears like the dawn” (ָחַרׁשֹכְּמו ְקָפָהׁהַנִּש אתֹז מִי), there is a well-known story about Rabbi Chiyah and Rabbi Shimon ben Chalafta who were walking in the Arbel valley in the early morning and saw the dawn breaking. The one said to the other, “So too the redemption of Israel will appear, first little by little; as it progresses it will appear more and more clearly.” In Midrash Rabbah on this verse, we find a more complete four-stage description of the redemption: “Initially it will come little by little, then it will sparkle on and on, then it will propagate more and more, then it will moisten more and more” (בַּתְּחִלָּה הִיא בָּאָה קִימְעָא קִימְעָא ,וְאַחַרְכָּך הִיא מְנַצְנֶצֶת וּבָאָה ,וְאַחַרְכָּך פָּרָה וְרָבָה ,וְאַחַרְכָּך מַרְטֶבֶת לֶכֶתֹוְהו). These four stages of the redemption correspond to the Four Parashot and how they lead up to the redemption from Egypt that we commemorate in Nissan (and ultimately to the true and complete redemption by the Mashiach).
Shekalim, which we associated with charity, collects little by little, as the sages say, “each and every penny [given to charity] combines to form a great sum.” We stimulate this through our gifts to the poor on Purim.
Zachor corresponds to the “sparkle” (נִצְנוּץ), which is cognate with “spark” (ץֹנִיצו) referring to the sparks of holiness that fell from the shattered kings of the World of Chaos, whose root is in the sefirah of knowledge of that world, the root of Amalek. The kings shattered because they were antagonistic to one another. We rectify this through our sending of food to one another on Purim.
Parah means heifer, but it also means “reproduction.” This is the actual description found in the third stage of redemption according to this midrash (פָּרָה וְרָבָה). There is a holy Name associated with reproduction, אלד (whose value is the same as “Jew,” יִהוּדְי). We stimulate this stage through our Se’udat Purim, which is known as Puria (פּוּרְיָא), with all the meanings associated with this word.
Finally, HaChodesh, which corresponds to wisdom represents renewal itself and is known as the wellspring of the infinite (נְבִיעַת הָאֵין ףֹסו), and a wellspring constantly moistens the earth around it, making it fertile, lush, and green. The wellspring of the infinite is found within the Torah, and on Purim we stimulate this stage of the redemption through the commandment to read the Scroll of Esther in the evening and in the day.
(based on a shiur given on 22 Adar 5751 and on Sod HaShem LiYerei’av, pp. 556-7)