The Torah draws a direct line between the tenth plague and a permanent commandment: "And the Lord killed every first-born... therefore, I sacrifice to the Lord every male first-born" (Exodus 13:15). The Mekhilta explains that this "therefore" carries the full weight of historical memory.
The sages established a precise correspondence. The firstborn of beasts are sacrificed in consideration of the firstborn beasts of Egypt that were killed during the tenth plague. And the firstborn of men — Israelite firstborn sons — are redeemed with silver in consideration of the Israelite firstborns who were saved that same night.
This is not mere symbolism. The rabbis understood the commandment as a perpetual debt of gratitude. On the night of the Exodus, God passed through Egypt and struck down every firstborn — both human and animal — while sparing the children of Israel. That act of selective mercy created an obligation that could never fully be repaid, only acknowledged.
Every time a firstborn animal is brought to the Temple and every time a father redeems his firstborn son through pidyon (redemption) haben, the memory of that terrible night is renewed. The plague was not random destruction. It was targeted justice. And the commandments that followed were designed to ensure that no generation of Israel would ever forget what it cost to be set free.