If I am A Christian, Why Do I Still Sin?

R. C. Sproul explains in his book, Faith Alone, that after we have obtained pardon from our sins, God regards us as righteous in His sight.  We are therefore justified, not by works, but by the mercy of God.  This is because Christ has imputed His righteousness to us and we are counted just by the imputation.

Martin Luther’s view of our being “at the same time just and sinner” (simul iustus et peccator) points out that we are justified while there is still sin in us.  According to Sproul:

“By this formula Luther did not mean that the sinner who is still a sinner is therefore an unchanged person.  The sinner who has saving faith is a regenerate person.  Regeneration effects real change in the person, but the change wrought by regeneration does not effect immediate perfection.

The regenerate person is now indwelled by the Holy Spirit.  Nevertheless he remains imperfectly just in himself.  The regenerate person is also in a real process of sanctification by which he is becoming just.  But he by no means reaches that point of perfect justness before God declares him perfectly just in Christ.

Those who possess saving faith necessarily, inevitably, and immediately begin to manifest the fruits of faith, which are works of obedience.  The ground of the person’s justification, however, remains solely and exclusively the imputed righteousness of Christ.  It is by His righteousness and His righteousness alone that the sinner is declared to be just and is really just in Him.” (pp. 102-103)

Therefore, as we were once sinners incapable of righteous acts – we are still sinners though sin does not reign in us.  We have become capable of righteousness and just acts in our lives even though we still experience difficulties with sin.  As the Apostle Paul writes:

“For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree with the law, that it is good. So now it is no longer I who do it, but sin that dwells within me. For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.

So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord!” (Romans7:15-25, ESV)

In these verses, Paul is describing a battle that every Christian finds inherent in his life in Christ.  The Christian is regenerate and Christ dwells in him, yet sin dwells in him as well.  The believer is now capable of growing in sanctification but perfect conformity is still out of his reach.  Therefore, let us be grateful for God’s mercy and live our lives to honor Him.