The teaching of the New Testament is not that God brings us to conversion and that later we may come to sanctification. Rather, it is that once a person is born again the very life of Christ is in that person, and their complete salvation is already a certainty. The saving work of God never stops short of glorification (Rom. 8:30). Therefore Paul can say to the believers at Philippi, ‘that he which has begun a good work in you will perform it until the day of Jesus Christ’ (Phil. 1:6).
Certainly the holiness of the Christian is imperfect, and far from complete, but already the believer has a new nature and a glorious change has begun that will leads to full conformity to Christ in glory.
It is a serious error to believe that a worldly-living person can be a true Christian. As a consequence of that error, the unregenerate have too often been given a false assurance of salvation and admitted into the membership of churches. When that happens, churches have to lower their standards to accommodate the tastes of the worldly, and before long what distinguishes the church from the world begins to disappear. The church is called to be as salt in the world, keeping society from utter putrefaction; but, says our Lord, if the salt becomes tasteless, ‘It is no longer good for anything, except to be thrown out and trampled under- foot by men.’ That, in a sentence, is the history of all churches whenever their membership and holiness part company.
What John Wesley said of the Methodists applies equally to all evangelical churches–
“I am not afraid that the people called Methodists should ever cease . . . But I am afraid, lest they should only exist as a dead sect, having the form of religion without the power. And this undoubtedly will be the case, unless they hold fast both the doctrine, spirit, and discipline with which they first set out.”
– Iain Murray