The role of works at the Final Judgment made simple:

Zip. Nada. Nothing. Not ever.

According to Mt. 7:21, the determining factor on the final day (or the purpose of the judgment therein) is entrance into the Kingdom of Heaven. The criterion of use by the LORD is whether or not a person has done the will of the father.

Since no one, to date, has done the will of the Father, it is necessary to trust on the bare fact of Christ's death and resurrection (that Christ has done the will of the Father FOR US and FOR OUR SALVATION). Or rather, it is necessary for the Christian to expect GRACE and MERCY on the final day (Jd. 21, 1 Peter 1:13). But if grace is to be given on the final day, it cannot be given on the basis of works, for then it would be a payment. And if mercy is to be delegated unto us, it would be foolish and meaningless to speak of JUST REWARDS. Mercy is given to the wicked, not the righteous. The righteous have need neither of mercy nor grace.

It is confounding and disastrous to place a role for works in the final judgment. To do so strikes at the very core of God's gospel and swallows it up in the law. For who will not immediately turn his attention towards the final day, forget the promise of the resurrection, and start working double time to earn a place in the heavens if this is precisely the way that God will deal with us? In short, the gospel will be lost forever in all of our glorious deeds.

Christians may be perfectly confident on the final day, perfectly confident, because they have for their very own badges the complete and total fulfillment of the law effected in Jesus Christ once for all. They need look nowhere else, indeed they would be knaves to do so. For what right-thinking man, after gazing on the blood of the lamb which bespeaks perfect righteousness, would turn aside and start trying to fulfill the law on his own? And who would trade in the very righteousness of God for his own paltry deeds?