Amalek's fall uncovers the bris and Torah

איתא בגמ' קימו וקבלו.

It is brought in the Gemara: "they upheld and accepted."

The Megillah's phrase "kiyemu vekiblu" (they confirmed and accepted) is the basis for the Gemara's teaching about Purim.

קיימו מה שקיבלו כבר.

They confirmed what they had already accepted.

At Purim, Bnei Yisrael willingly reaffirmed the Torah they had first received at Sinai — re-accepting it now out of love.

שבפורים זמן קבלת התורה.

For Purim is a time of accepting the Torah.

Purim is itself a season of kabbalas haTorah, a renewed receiving of the Torah.

כמו שאחר מלחמת עמלק ברפידים באו להר סיני לקבל התורה.

Just as after the war with Amalek at Refidim they came to Har Sinai to receive the Torah,

The historical pattern: immediately following the battle against Amalek at Refidim, Bnei Yisrael proceeded to Sinai to receive the Torah.

כן לעולם אחר מפלת עמלק יש קבלת התורה.

so too always, after the downfall of Amalek there is an acceptance of the Torah.

This is a timeless principle: whenever Amalek is defeated, the way opens to receive the Torah anew — as happened again at Purim with the fall of Haman.

כי מילה קדמה לתורה.

For milah precedes the Torah.

The bris milah is the necessary prerequisite that comes before receiving the Torah.

והיא שער השמים כמ"ש מי יעלה לנו השמימה ר"ת מילה.

And it is the gate of heaven, as it is written: "Who will ascend for us to the heavens" — whose initial letters spell "milah."

Milah is the gateway upward; the verse "Mi Yaaleh Lanu Hashamaymah" begins with the letters of "milah," showing that circumcision is what opens the heavens to a person.

שעי"ז זכו לקבלת התורה מן השמים.

For through this they merited to receive the Torah from heaven.

It is precisely through the gateway of milah that Bnei Yisrael became worthy to receive the heavenly Torah.

ואותו הרשע עמלק הוא ערלה דחפיא ברית כמ"ש לעיל פ' יתרו מזה.

And that wicked one, Amalek, is the orlah (foreskin) that covers over the bris, as was said above in Parshas Yisro regarding this.

Amalek represents the orlah — the covering that conceals and blocks the holy bris — the force that stands opposed to the gateway of milah.

ולכן אחר מפלת עמלק מתגלה הברית מילה וזוכין אל התורה:

Therefore, after the downfall of Amalek, the bris milah is revealed and one merits the Torah.

Once Amalek — the "covering" — is removed, the holy bris is uncovered and revealed, and through that open gateway Bnei Yisrael attain the Torah.

Summary: Purim is a renewed acceptance of the Torah, following the timeless pattern that the defeat of Amalek leads to kabbalas haTorah. Amalek is the orlah that covers and blocks the bris milah — the very gateway to heaven through which the Torah is received. When Amalek falls, the bris is uncovered and the path to the Torah opens.