The following insight also comes from Rav Eliyahu Baruch Finkel.
By the laws of “Eglah Arufah” [the decapitated calf], the Torah records the declaration of the Beis Din who proclaim:כפר לעמך ישראל אשר פדית - “Atone for Your nation Yisrael that you redeemed” (21:8). What exactly is the nuance of the expression אשר פדית ? The simple understanding is that the expression refers to all of Klal Yisrael in all generations. The Ribbono Shel Olam took us out of Mitzrayim (מבית עבדים פדיתנו) therefore we (in all generations) are the nation of the Almighty, whom He has redeemed!
The Ibn Ezra interprets differently. He says that, כפר לעמך ישראל אשר פדית is not referring to Jews in general. It is referring specifically to that generation of Jews who were redeemed from Mitzrayim. The Beis Din proclaims: Grant atonement now to that generation of Jews that You took out from Mitzrayim then! However, this pasuk is referring to a time that was hundreds of years after Yetzias Mitzrayim. What does the Ibn Ezra mean? Why do Klal Yisrael who came out
