What is Justification?
Those whom God effectually calls He also freely justifies.He does this, not by infusing righteousness into them, but by pardoning their sins, and by accounting and accepting them as righteous,not for anything done in them or by them, but for Christ's sake alone. They are not justified because God imputesas their righteousness either their faith itself, or the act of believing, or any other act of obedience to the Gospel. They are justified by God imputing Christ's active obedience to the whole Law and His passive obedience in death. By faith they receive and rest on His righteousness, and this faith they do no have of themselves for it is the gift of God.
Faith which receives and rests on Christ and His righteousness is the sole instrument of justification.Yet it is never alone in the person justified, but is always accompanied by all the other saving graces; it is not a dead faith, for it functions by love.
By His obedience and death, Christ fully discharged the debt of all those who are justified. By His sacrifice in the blood of His cross, He underwent in their place the penalty due to them, so making an appropriate, real, and full satisfaction of God's justice on their behalf.Yet their justification is entirely of free grace, because He was given by the Father for them,and His obedience and satisfaction was accepted in their place,both actions being done freely, and not because of anything in them.So both the exact justice and the rich grace of God are glorified in the justification of sinners.
From all eternity God decreed to justify all the elect,and Christ in the fullness of time died for their sins, and rose again for their justification.Nevertheless they are not justified personally until the Holy Spirit in due time actually applies Christ to them.
God continues to forgive the sins of those who are justified;and although they can never fall from the state of justification,yet they may fall under God's fatherly displeasure because of their sins. In that condition they will not usually have fellowship with Godrestored to them until they humble themselves, confess their sins, ask for pardon, and renew their faith and repentance.
The justification of believers under the Old Testament was in all these respects exactly the same as the justification of believers under the New Testament.