"So this I say, and affirm together with the Lord, that you walk no longer just as the Gentiles also walk, in the futility of their mind, being darkened in their understanding, excluded from the life of God because of the ignorance that is in them, because of the hardness of their heart." (Ephesians 4:17,18)
It is an amazing thing that so many who are Christians still continue to live their lives (walk) just as unbelievers (Gentiles), in the futility of their minds, darkened in their understanding, excluded from the life of God because of the ignorance that is in them, because of the hardness of their heart. To be sure, there are many who lie, claiming to belong to Christ, who are not really Christians, and are simply living consistent with their ignorance; "If we say that we have fellowship with Him (that we are Christians) and yet walk in the darkness, we lie and do not practice the truth."(1 John 1:6)
And yet their are also real Christians who allow themselves to be conformed to the unbelieving world in how they think, where they go, what they do and say; "And do not be conformed to this world, but be transformed by the renewing of your mind, so that you may prove what the will of God is, that which is good and acceptable and perfect."(Romans 12:2) So how do you stop being conformed to the unbelieving world and be transformed to the new life in Christ? The Apostle Paul urges Christians to first totally dedicate their lives-- body, soul and mind to God; "Therefore I urge you, brethren, by the mercies of God, to present your bodies a living and holy sacrifice, acceptable to God, which is your spiritual service of worship."(Romans 12:1)
This is Jewish temple sacrifice language that would be very familiar and a good word picture for Paul's readers. When a Jew offered a sacrifice upon the alter in the temple, they were to do so completely and permanently. A partial sacrifice or one that was later taken back after placing it upon the alter, would obviously not be acceptable to God. In the same way, God requires true Christians to worship Him by presenting their minds and bodies completely and permanently as a living and holy sacrifice.
Salvation or justification happens immediately when one hears and believes the gospel of our Lord Jesus Christ. The process of transformation or sanctification then begins and continues throughout the physical life of a believer. The transformation happens as the Holy Spirit, who indwells believers, instructs us in God's word (the Bible), renewing our minds and conforming us more each day to the life and character of our Lord Jesus Christ. It is God who does the transformation as we submit to Him in total trust and obedience.
Christians who continue to live lives conformed to the godless, unbelieving world, are like butterflies who try to crawl back into the cocoon and live like the lowly moth they once were. If you really are a Christian, you are a new creature in Christ. Old things have passed away and you are indeed a new person in Christ who is being transformed by the renewing of your mind. Leave that old cocoon-- It's time to Fly! Maranatha!