Conversion is an integral idea in the Bible. It is probably the least understood principle by the general populace. The idea of conversion has its roots in the Old Testament. Its usage there suggests it signifies "to turn back" "to go back" "to come back" " or to "return." It is also associated with the Hebrew concept "to be sorry" or "to regret."
In the New Testament there are two major words associated with the idea "to turn." Those words are, epistrepho and metanoeo. The second word and its derivatives indicate a renewal of mind and heart, or what we would call "heart-felt repentance."
A key passage in the New Testament is Matthew 18:3 where it reads, "...truly, I say to you, unless you turn and become like children, you will never enter the kingdom of heaven." (ESV) The New English Bible reads, "Unless you turn around..."
In bible theology, conversion is defined as the human response to regeneration, or the re-birth of the spirit in man by the Holy Spirit. The Holy Spirit according to John 3:8 is the means by which a human being who is previously born "spiritually dead" is made alive. The human response once made alive by the Holy Spirit is to respond by repenting, or by turning from sin and turning to God. The process of regeneration and conversion is an instantaneous process enabled solely by the grace of God. The Holy Spirit creates spiritual life in a soul and that soul responds by turning from condemning and damming sin and by turning to God based on the atoning work of Jesus Christ.
Conversion is the incursion of divine grace into human life, the resurrection from spritual death to eternal life. It can be understood that an individual is passive in regernation and active in conversion. We must be careful at this point to make a distinction - we are only active on the basis of grace and only through the power of grace. An individual cannot produce salvation. However, once the spiritual eyes are opened via the Holy Spirit generating spiritual life within an individual, the result will always be conversion; a willing turning away from sin and a turning to God. It also must be pointed out very carefully that conversion is the sign of our justification before God, however, it is not the cause nor condition of our justification.
Conversion is an event which signifies the action of the Holy Spirit upon an individual which results in an individual responds to the atoning work of Jesus Christ. An individual cannot be converted by his or her own power. We cannot manufacture, conjure up, work up, or otherwise manipulate regeneration or conversion. Both are solely the work of God through the Holy Spirit by grace as a result of the death, burial, and resurrection of Jesus Christ. Without conversion no man will see God nor enter the kingdom of heaven.