Jesus is himself the first person to retell the story of Israel with his death and resurrection at its center. Peter, both in Acts and in his First Letter, retells that story too. And although the Bible never explains how exactly Jesus' death saves us, it regularly uses the word "ransom" to describe Jesus' death on the cross. And more often than not the words that we read in English as "redeem, redemption" are really the same Greek word as "ransom". Even though we often tend to lump our "redeeming" with words like "forgiving" or "satisfying" or "rescuing", it first and foremost is buying word, a marketplace word, a word for trading away your costly valuables to release an enemy's victims from their slavery. And that is a favorite image of the first Christian centuries: giving up a Son to free us slaves.
O wonder of your humble care for us!
O love, O charity beyond all telling,
to ransom a slave you gave away your Son!
O truly necessary sin of Adam,
destroyed completely by the Death of Christ!
O happy fault that earned so great, so glorious a Redeemer!