Rashi on Exodus 21:30/רש"י על שמות כ״א:ל׳

1אם כפר יושת עליו WHEN THERE BE SET ON HIM A RANSOM — This אם is not conditional (i. e. it does not mean “if” the heirs feel inclined to set on him a ransom) but it has the same meaning as in (Exodus 22:24) “When (אם) thou lendest money” where it has the meaning of אשר, “when” (for it is a duty to lend money to the poor and it is not optional). It is the law regarding him that the court should set on him a ransom.

2ונתן פדיון נפשו HE SHALL GIVE THE RANSOM OF HIS SOUL — the value of the injured person; this is the view of R. Ishmael, R. Akiba, however, says that it means the value of the person who caused the injury (Mekhilta).