Soteriology is the branch of dogmatic theology that deals with salvation through Christ. In the Catholic tradition, the initial grace of justification and forgiveness, and thereby, eternal life, and divine life cannot be merited by our natural selves but is a free gift of God. By his crucifixion and death on the Cross, Jesus has atoned for our sins once and for all and has reconciled the world to God. He alone has produced this grace for everyone through his single sacrificial offering of himself. In the words of John the Baptist, "Behold the lamb of God who takes away the sins of the world" (John 1:29). Thus, the Catholic Church has taught from the earliest times that we are saved from the consequences of sin by grace through faith in Christ working through love (cf. Eph 2:8-9; Gal 5:5-6).
Suffice it to say, soteriology is defined as "that part of Christology which treats of Christ's work of salvation. It covers the study of man's fall in Adam and the sins of mankind, which needed a Savior, the doctrine of grace by which the guilt and consequences of sin are removed, and especially the twofold mystery of Christ as Redeemer and Mediator of the human race. (Etym. Greek sōtērion, deliverance; from sōtēr, savior; from sōzein, to save; from saos, safe."
- Fr. John Hardon's Modern Catholic Dictionary
For what saith the Scripture that Abraham believed God
and it was counted unto him as righteousness (dikaiosunen).
Romans 4, 3
Therefore, we conclude that a man is justified (dikaiousthai) by faith
without the deeds of the law.
Romans 3, 23
Was not Abraham our father justified (edikaiosthe) by works
when he had offered his son Isaac up to God on the altar?
James 2, 21
You see then that how by works a man is justified (dikaiotai),
and not by faith only.
James 2, 24 [KJV]
By your stubbornness and impenitent heart, you are storing up wrath for yourself on the day of wrath
and revelation of the just judgment of God, who will repay everyone according to his works: eternal life to
those who seek glory, honour, and immortality through perseverance in good works, but wrath and fury to
those who selfishly disobey the truth and obey wickedness.
Romans 2, 5-8
There is no partiality with God. All who sin outside the law
will also perish without reference to it, and all who sin under the
law will be judged in accordance with it. For it is not those who
hear the law who are just in the sight of God; rather those who observe
the law will be justified.
Romans 2, 11-13
For all have sinned and do need the glory of God. Being justified
by his grace through the redemption, that is of Jesus Christ, whom
God has proposed to be a propitiation, through faith in his blood,
to the shewing of his justice, for the remission of former sins.
Romans 3, 23-25
Therefore, since we have been justified by faith,
we have peace with God through our Lord Jesus Christ.
Romans 5, 1
What does it profit, my brethren, if a man says he has faith but
has not works? Can his faith save him? If a brother or sister is
ill-clad and in lack of daily food, and one of you says to them, “Go
in peace, be warmed and filled,” without giving them the things
needed for the body, what does it profit? So faith by itself, if it has
no works, is dead.
James 2, 14-17
You see that a man is justified by works and not by faith
alone. And in the same way was not also Rahab the harlot
justified by works when she received the messengers and sent them
out another way? For as the body apart from the spirit is dead,
so faith apart from works is dead.
For the Son of man is to come with his angels in the glory of his
Father, and then he will repay every man for what he has done.
Matthew 16, 27