Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ. Ephesians 4:13
The work of God is not finished in the heart and life of the new believer when the first act of inward adjustment has given him a sense of cleansing and forgiveness, peace and rest for the first time in his life!
The Spirit would go on from there to bring the total life into harmony with that blissful “center.” This is wrought in the believer by the Word and by prayer and discipline and suffering.
It could be done by a short course in things spiritual if we were more pliable, less self-willed and stubborn; but it usually takes some time before we learn the hard lessons of faith and obedience sufficiently well to permit the work to be done within us with anything near to perfection.
In bringing many sons unto glory God works with whatever He has in whatever way He can and by whatever means He can, respecting always His own gift to us, the freedom of our wills. But of all means He uses, the Bible is the best.
The Word of God well understood and religiously obeyed is the shortest route to spiritual perfection, and we must not select a few favorite passages to the exclusion of others. Any tinkering with the truth, any liberties taken with the Scriptures, and we throw ourselves out of symmetry and invite stiff discipline and severe chastisement from that loving Father who wills for us nothing less than full restoration to the image of God in Christ!