The Korban Pesach is meant to commemorate the miracle of the Jewish households being “passed over” in Egypt.
But why were they ever at risk? The plagues were punishments for enslaving the Jews. If the first nine plagues were targeted at Egyptians, why should the tenth have been any different, requiring being “passed over”?
Why is the salvation of the Jewish firstborn different that it required spreading blood on their doors, and later generations then had to commemorate this act by eating the Korban Pesach?
R’ Yitzchak Blaser explains that the Gemara in Yuma 86a teaches that even though repentance alone does not usually atone for a violation of a negative commandment; nevertheless, on Yom Kippur the flood of mercy is so great that if a person repents, he can have attain forgiveness – even if they might not deserve it!
The Midrash says: Woe to the wicked, who convert Divine mercy to strict justice – מדת הדין into מדת הרחמים.
R’ Yitzchak Blaser explains that what the Midrash is the reverse application of the Gemara – if a person had a chance to erase sins they couldn’t get rid of an entire year, and turned their back on such an opportunity, the disdain shown for the mercy offered rebounds, and it becomes strict justice.
Although the Jews had served the Egyptian idols, it hadn’t been out of choice. But with the slavery effectively over, they had the chance to throw off any trace of idol worship and show their commitment and dedication to Him by taking a lamb, an Egyptian deity, and publicly display that they did not accept
If they turned their backs on this ideal opportunity they would have incurred Hashem’s wrath and מדת הדין.
The other plagues were specific punishments that the Jews were not deserving of, but the 10th plague was not “just” a punishment for the Egyptians, unlike the previous plagues, it had a secondary function. The first nine plagues were punishments that they revealed Hashem’s hand in nature; the Jews had done nothing to be punished in this way – they were victims. But here they had an opportunity to throw off the yoke of idol worship, and had they not taken their chance, they would have incurred a מדת הדין – putting themselves in danger.
The Korban Pesach we take is a remembrance of the kindness we were shown, that led to us being saved. The Targum actually translates ופסחתי (Shemos 14:13) as a word meaning “compassion”.