Impute: To think of as belonging to someone, and therefore to cause it to belong to that person. God “thinks of” Adam’s sin as belonging to us, and it, therefore, belongs to us, and in justification, he thinks of Christ’s righteousness as belonging to us and so relates to us on this basis.
The Father, because of his love for human beings, sent his Son (who offered himself willingly and gladly) to satisfy God’s justice, so that Christ took the place of sinners. The punishment and penalty we deserved was laid on Jesus Christ instead of us, so that in the cross God’s holiness and love are manifested.
Redemption: Christ’s saving work is viewed as an act of “buying back” sinners out of their bondage to sin and to Satan through the payment of a ransom (though the analogy should not be pressed to specify anyone to whom a ransom was paid).