“Those whom God effectually calls, He also freely justifies; not by infusing righteousness into them, but by pardoning their sins, and by accounting and accepting their persons as righteous; not for any thing wrought in them, or done by them, but for Christ’s sake alone; nor by imputing faith itself, the act of believing, or any other evangelical obedience to them, as their righteousness; but by imputing the obedience and satisfaction of Christ unto them, they receiving and resting on Him and His righteousness by faith; which faith they have not of themselves, it is the gift of God… God does continue to forgive the sins of those that are justified; and although they can never fall from the state of justification, yet they may, by their sins, fall under God’s fatherly displeasure, and not have the light of His countenance restored unto them, until they humble themselves, confess their sins, beg pardon, and renew their faith and repentance. The justification of believers under the Old Testament was, in all these respects, one and the same with the justification of believers under the New Testament.” – The Westminster Confession of Faith, Of Justification, Chapter 11:1,5,6, Original Edition, 1647.
“This one and firm rock, which we call the doctrine of justification is the chief article of the whole Christian doctrine, which comprehends the understanding of all godliness… if this article stands, the Church stands; if it falls, the Church falls.” – Martin Luther, Commentary on Galatians, 1538.
“We explain justification simply as the acceptance with which God receives us into His favour as righteous men. And we say that it consists in the remission of sins and the imputation of Christ’s righteousness.” – John Calvin, Institutes of the Christian Religion, 3:11:2.