Justification (theology)
Justification, in Christian theology, 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. To Protestants righteousness from God is credited to the sinner's account through faith alone, without works.
The means of justification is an area of significant difference between Catholics/Eastern Orthodox and Protestants. Broadly speaking, Catholic and Orthodox Christians distinguish between initial justification, which in their view occurs at baptism, and permanent justification, accomplished after a lifetime of striving to do God's will. Most Protestants 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. Catholics and Eastern Orthodox use Galatians 5:19-21 and Matthew 19:17 to support their belief that justification is kept through avoiding grave sins. Justification is seen by Protestants as being the theological fault line that divided Catholic from Protestant during the Protestant Reformation.
Read more about Justification (theology): Early Church and Justification, Comparison of Traditions