A total change in how a person lives and thinks. For Christians, this means a change from a way of living that ignores God to one in which the person is submitted to Christ. Conversion is the result of repentance.
Conversion in the Old Testament
In the Old Testament, conversion is basically a turning or returning from one’s former course of life toward the Lord, the God of Israel. Israel often had to return to their God (Deuteronomy 4:30), either as individuals (Psalm 51) or as a nation (Jeremiah 4:1). Foreign nations needed to turn to God for the first time (Psalm 22:27). The defining feature is that one turns away from doing evil acts (Jeremiah 26:3; 36:3; Ezekiel 18:21, 27; 33:9, 11). Conversion is turning from a life of disloyalty to God to a life of obedience to God (Isaiah 10:20–21; 14:2; Jeremiah 34:15; Hosea 14:4). Conversion means a change in inward orientation that is demonstrated in a changed lifestyle.
Conversion in the New Testament
In the New Testament, John the Baptist begins the call to conversion (Matthew 3:2; Mark 1:4; Luke 3:3). He gives a prophetic call for people to change their minds (which is the root meaning of the Greek term) because of the nearness of God’s kingdom. This change of life must include a change in actions to prove its reality (Matthew 3:8; Luke 3:8). Jesus preached the same message (Matthew 4:17; Mark 1:15). He also said that since the kingdom of God had arrived in his person, obedience to him was part of the good news of conversion. Yet it could also be bad news, for one would be condemned if he failed to make this radical change (Matthew 11:20; Luke 13:3–5). Conversion is radical but also simple. It requires the simplicity of a child who commits their whole self, not the calculating self-protectiveness of the adult (Matthew 18:3). The contrast is between an adult's cautious, self-preserving attitude and the simple, sincere trust and openness of a child.
Outside the gospels, conversion is not a frequently used term except in the book of Acts. When used in the book of Acts, conversion
forms the call to commitment at the most important part of evangelistic sermons (2:38; 3:19; 8:22),
describes the commitment of new Christians to the Lord (9:35; 11:21), and
pictures the change of life as a turning from darkness to light (26:18–20).
When referring to conversion, later writers
remember conversion (2 Corinthians 3:16),
worry about Christians converting to paganism or Judaism (Galatians 4:9), and
call for the reconversion of Christians who have left the faith and are in danger of judgment (James 5:19–20; Revelation 2:5, 16, 22; 3:19).
As in the Old Testament, and the preaching of John and Jesus, conversion has three factors.
Conversion is a turning from something, which includes specific sins, false gods, or simply a life lived for oneself (1 Thessalonians 1:9; Revelation 9:20–21; 16:11).
Conversion is a product of the will of God and his gracious working in the world (Acts 11:18; Romans 2:4; 2 Corinthians 7:10; 2 Timothy 2:25; 2 Peter 3:9).
Conversion is a turning to someone, a commitment of one’s whole life to God in Jesus Christ (Acts 14:15; 1 Thessalonians 1:9; 1 Peter 2:25).
It is thus a total reorientation, whether spectacular or undramatic, sudden or gradual, emotional or calm, in which a person transfers his or her total allegiance to God.