Rebbi — Rabbi Yehudah HaNasi — taught that "nefesh (the vital soul) for nefesh" — "a life for a life" — means monetary compensation, not literal execution. The Torah is requiring the payment of a life's monetary value, not the taking of the striker's life.
But perhaps "nefesh" should be understood literally — an actual life for a life? Rebbi rejected this through a gezeirah shavah, a verbal analogy. The word "imposed" (yashith) appears in this verse, and the same root (yushath) appears in (Exodus 21:30), which deals explicitly with monetary ransom. Just as "imposed" in the ransom context clearly means monetary payment, "imposed" here also means monetary payment.
This interpretation has dramatic implications. The famous principle of "a life for a life" — which sounds like an endorsement of capital punishment or at least strict retaliatory justice — is read by Rebbi as a financial obligation. You do not pay with your own life. You pay with money equivalent to the value of the life lost.
This aligns with the broader rabbinic understanding of "eye for an eye" as monetary compensation rather than literal bodily retaliation. The Torah's language of equivalence — eye for eye, life for life — establishes the measure of what is owed, not the method of payment. The currency is always money. The victim's family receives financial redress. The principle is proportional justice, not symmetrical violence.