Redemption

the purchase back of something that had been lost, by the
payment of a ransom. The Greek word so rendered is
"apolutrosis", a word occurring nine times in Scripture, and
always with the idea of a ransom or price paid, i.e., redemption
by a lutron (see Matt. 20:28; Mark 10:45). There are instances
in the LXX. Version of the Old Testament of the use of "lutron"
in man's relation to man (Lev. 19:20; 25:51; Ex. 21:30; Num.
35:31, 32; Isa. 45:13; Prov. 6:35), and in the same sense of
man's relation to God (Num. 3:49; 18:15).

There are many passages in the New Testament which represent
Christ's sufferings under the idea of a ransom or price, and the
result thereby secured is a purchase or redemption (compare Acts
20:28; 1 Cor. 6:19, 20; Gal. 3:13; 4:4, 5; Eph. 1:7; Col. 1:14;
1 Tim. 2:5, 6; Titus 2:14; Heb. 9:12; 1 Pet. 1:18, 19; Rev.
5:9). The idea running through all these texts, however various
their reference, is that of payment made for our redemption. The
debt against us is not viewed as simply cancelled, but is fully
paid. Christ's blood or life, which he surrendered for them, is
the "ransom" by which the deliverance of his people from the
servitude of sin and from its penal consequences is secured. It
is the plain doctrine of Scripture that "Christ saves us neither
by the mere exercise of power, nor by his doctrine, nor by his
example, nor by the moral influence which he exerted, nor by any
subjective influence on his people, whether natural or mystical,
but as a satisfaction to divine justice, as an expiation for
sin, and as a ransom from the curse and authority of the law,
thus reconciling us to God by making it consistent with his
perfection to exercise mercy toward sinners" (Hodge's Systematic
Theology).