There is a faith-sustained holiness that Paul wants his converts to have on the day of Christ — the day of his return, when the dead in Christ will be raised (1 Corinthians 15:23). This holiness (which he also calls “blamelessness” and “guiltlessness” and “being above reproach” and “purity”) is certain through God’s faithfulness, contingent on persevering faith, and dependent on human agency.
Paul is certain that God will work this persevering faith and holiness in his converts for the day of Christ. This is part of God’s faithfulness.
May the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ. He who calls you is faithful; he will surely do it. (1 Thessalonians 5:23–24)
You wait for the revealing of our Lord Jesus Christ, who will sustain you to the end, guiltless in the day of our Lord Jesus Christ. God is faithful, by whom you were called into the fellowship of his Son, Jesus Christ our Lord. (1 Corinthians 1:7–9)
I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ. (Philippians 1:6)
That’s Paul’s expectation and confidence for his converts. But the certainty of their perseverance in faith and holiness is not automatic. That is, it does not lie within the converts in such a way that their faith and holiness will survive without God’s work in them.
The Christian convert as God’s new creation (2 Corinthians 5:17) does not contain the power to persevere. Rather, the new creation contains the link to the one who daily provides the power to persevere. And that link is sure, Paul says, because it is sustained decisively by God, not man. This is why Paul insists, “God is faithful; he will surely do it” (1 Thessalonians 5:24; cf. 1 Corinthians 1:9).
Nevertheless, though it is certain for all who are new creatures in Christ, Paul tells believers, “You . . . [Christ] has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him, if indeed you continue in the faith” (Colossians 1:21–23).
The holiness that we are to have at the day of Christ’s coming is contingent on continuing in the faith. This contingency does not contradict certainty. God is faithful; he will do it. But no believer should think that he will be ready to meet Christ if he does not “continue in the faith.”
God’s faithfulness is experienced in his continually awakening in us the grace to keep believing. He keeps us. And he does it by giving us the passion to treasure him and pursue holiness.
Paul does not simply watch this dynamic play out in the lives of his converts. He prays for them. And what he prays is that they will, in fact, be pure and blameless on the day of Christ.
It is certain they will arrive safely in faith and holiness at the day of Christ. That arrival is contingent on persevering faith. And Paul’s prayers are the agency God uses to bring them safely home.
It is my prayer that your love may abound more and more, with knowledge and all discernment, so that you may approve what is excellent, and so be pure and blameless for the day of Christ. (Philippians 1:9–11)
May the Lord make you increase and abound in love for one another and for all, as we do for you, so that he may establish your hearts blameless in holiness before our God and Father, at the coming of our Lord Jesus with all his saints. (1 Thessalonians 3:12–13)
Therefore, let the truth of Paul’s certainty make us sure. Let the truth of contingency make us serious. And let the truth of agency make us to surround ourselves with praying brothers and sisters who intercede for our faith and holiness.