The Verdict of Innocent in the Judgment Hour
For us to say that we are justified by faith alone in the Judgment Hour means that we repentant sinners who believe in Jesus are declared innocent, sinless, perfect and forgiven before the holy Law of God because Jesus, the sinless One, took the guilt, punishment, and death that we deserve. God imputed our sins to Him, the innocent One, so that we, the guilty ones, may have the sinless life of Jesus imputed to us. He was condemned for sins in which he had no part so that we may be declared innocent by His perfect life in which we had no part.
The word of God tells that we are all born as sinners by nature and that the Law of God condemns us and declares us worthy of death. But Jesus stepped in between the Law and us and took our place and bore that death penalty. This is what happened at the cross. The innocent One was suffering for our sins, in our place. Now God calls all sinners to believe that Good News of what Jesus has done for all sinners in bearing their punishment. Those who repent and believe that their sins are forgiven because of what Jesus did on the cross are justified (declared sinless and not guilty) before the judgment bar of God. Paul states this clearly in Ephesians 2:1-10—
"And you...who were dead in trespasses and sins...were by nature the children of wrath. But God who is rich in mercy because of His great love with which He loved us, made us alive together with Christ....For by grace you have been saved (justified) through faith and that not of yourself (because of our goodness) it is the gift of God, not of works (our holy living) lest anyone should boast. For we are His workmanship created for good works (our holy living) which God prepared beforehand that we should walk in them."
To summarize the text: All of us are wretched, condemned sinners, but God loves us and in the Person of our Lord Jesus Christ infinitely humbled Himself and took upon Himself human nature to die on the cross for us and pay for our sins. All who believe in Jesus' atoning death for us are justified (accounted righteous and saved) by faith in Him not because we have done good works of sanctified living. Those who believe in Jesus are declared to be God's children who then begin to do good works of love which glorify God. But these good works never justify us but rather are the fruit of having been justified by faith alone.
God loves us and He accepts us as His sons and daughters because of Jesus' perfect life, not because we are perfect. None of us are sinless in this life. He wants us to begin to keep His Law of love but not so that we can be saved by our keeping of His Law. All of our lives as Christians we continually fall short of perfect obedience and perfect love. We sin in word, thoughts, and deeds but we repent and continually plead the merits of Christ and God continually imputes the perfection of Jesus to us. This is the experience of even the most mature and holy of God's people. We all confess the sinfulness of our nature and confess that in and of ourselves we deserve to suffer and die for our sins. But we Christians are always being justified by faith and we have peace with God through Jesus Christ our Lord. "Be of good cheer, thy sins be forgiven thee."
Thus we see that we are continually justified by faith, at the beginning of our life in Christ and all along the way of life we are always relying upon God's mercy and grace in Christ. The only way we can be lost is if we stop acknowledging our sins and our need of Christ's blood to cover our imperfections and we return to a life of unbelief in Christ and we return to a life of willful disregard for the moral Law of God and willful, unrepentant disobedience of God's holy commandments. This means that if we ever begin to believe that we are sinless and no longer need God's mercy (Perfectionism / Legalism), we have fallen from justification by faith. On the other hand if we ever begin to believe that we no longer need to obey God's Ten Commandments (Antinomianism / Lawlessness) and begin to willfully, without repentance, and continually sin against God, we have fallen from justification by faith as well.
Justification by faith alone is the true Gospel which the true Holy Spirit seals into the hearts of God's people. This is the sealing message of God that proclaims the true Jesus Christ our Lord and Savior who will protect us and cover us during the coming time of trouble when the Antichrist powers of the Enemy will declare that no man may "buy or sell" unless he has the mark of the Beast, the observance of the false Sunday Sabbath which is the invention of the Man of Sin (the sign of justification by works).
Many of the Protestant reformers did not fully understand all that was to be accomplished in the Reformation. God lead them to make giant strides in the recovery of the Gospel of Justification by Faith Alone. The reformers were greatly blessed with the light of heaven which God shone upon their pathway.
But Martin Luther certainly never claimed to be the final word when it comes to understanding God's word and dividing it rightly. Luther was wrong to say that the epistle of James is an epistle of straw. (James is speaking of our justification before men which must be a faith that works by love which motivates us to fill our lives with good works for the benefit of our fellow man. For faith that does not yield the fruit of service to God and man is a vain faith which even the devils believe)
But it is so easy for us to sit in our comfortable homes discussing the great themes of salvation and pass judgment upon this or that teaching with total freedom from fear for life or limb. Every time the reformers picked up pen in hand, they took their life in hand as well. We must tread carefully when we humbly approach the great creeds of Protestantism which were written with the very life blood of so many martyrs who defied the Beast and his Image and boldly proclaimed that we are accepted before the Law of God because of a righteousness that is in heaven at the right hand of God in the Person of our Lord Jesus Christ.
We have access to complete libraries containing mountains of information, dialogue, discussion, and historical background which enable us to look over the theological landscape and make decisions which are much more informed than those who lived when the printing press was in its infancy, knowledge of the original languages of scripture was rare, and rapid communication was unheard of and undreamed of in today's terms.
The Holy Spirit is being poured out in latter rain power in the proclamation of the pure Gospel of Christ and His imputed righteousness for all repentant sinners who look to Calvary. The restoration of the temple of truth is nearing completion and the Antichrist is soon to receive a deadly wound from which he will never be healed. All heaven is astir and the angels are loosing their hold on the winds of strife. Justification by faith "alone" in the sin-pardoning Savior in this the hour of God's judgment will swell to one final glorious revelation of the grace of God who justifies the ungodly in Christ and for the sake of Christ and His infinite imputed righteousness to all who believe.
To briefly touch on the matter of whether "alone" is a valid insertion to the Biblical phrase "justification by faith" we can simply say this. Does our sanctification and holiness of life (even of the most mature Christian) ever enable us to stand before the Law of God and be measured by the righteousness of the Law? No! Why? Because the Law demands the very righteousness of God to meet its high and holy demands. This not even the holiest saint who ever lived can bring to the Law as a sanctified life pure enough to pass its scrutiny.
Nothing in my hand I bring,
simply to the Cross I cling.
Rock of Ages, cleft for me,
let me hide myself in Thee.
Are we justified by faith alone? Absolutely! Does justifying faith in Christ bring the gift of the indwelling Holy Spirit to begin to write the Law of God in our hearts? Absolutely. Does the work of the Holy Spirit in our hearts ever justify us? Never!
Come quickly, Lord Jesus we are complete in Thee.