In Christian theology, justification is God's act of removing the guilt and penalty of sin while at the same time declaring a sinner righteous through Christ's atoning sacrifice.
The means of justification is an area of significant difference between Catholicism, Orthodoxy and Protestantism, even within the latter. In Lutheranism and Calvinism, righteousness from God is viewed as being credited to the sinner's account through faith alone, without works. Broadly speaking, Catholic, Methodist and Orthodox Christians distinguish between initial justification, which in their view ordinarily occurs at baptism, and final salvation, accomplished after a lifetime of striving to do God's will (sanctification). Many Protestants, such as Lutherans and Calvinists, believe that justification is a singular act in which God declares an unrighteous individual to be righteous, an act made possible because Christ was legally "made sin" while on the cross (2 Cor 5:21). Justification is granted to all who exercise faith, and that is viewed as a gift from God (unmerited favour) by Lutherans and Calvinists, who use Eph 2:8, as well as Acts 16:14 and Phil 1:29 to support that belief. In Methodism, justification refers to "pardon" and "the forgiveness of sins" and sanctification is the consequent process that together, will ultimately lead to one's salvation. Catholics, Orthodox and Methodists use James 2:14-26, Galatians 5:19-21 and Matthew 19:17 to support their belief that justification is kept through avoiding grave sins. Justification is often seen as being the theological fault line that divided Catholic from the Lutheran and Reformed traditions of Protestantism during the Reformation.