The biblical definition of repentance “metanoia” as used in the Greek bible is quite different from our definition of the English word “repentance” we use today. If this isn’t understood correctly, it can lead one far astray in his study of Bible doctrine.
Our English definition of repentance is “deep sorrow, compunction, or contrition for a past sin, wrongdoing, or the like,” or “regret for any past action.”
However, the biblical definition of repentance is “to change one’s mind,” or “to change one’s purpose,” or “to change direction.” We can think of it like the mental equivalent of what a soldier does when he is given the “about-face” command. He is facing in one direction, and he turns completely around by 180 degrees in order to face the exact opposite direction. So, for example, Acts 20:21 says, “I have declared to both Jews and Greeks that they must turn to God in repentance and have faith in our Lord Jesus.” This means that the sole requirement for being saved is to have faith in Christ. This happens when we “turn to God in repentance.” Our minds were initially turned away from God–toward man (Romans 5:12-21). However, we changed our minds (repented) and pointed our minds in the opposite direction, toward God.
But please understand that this biblical repentance for salvation has nothing to do with feeling sorrow, compunction, contrition, regret, or remorse. (Although 2 Corinthians 7:9-10 tells us that sorrow can lead to repentance.) Sometimes people are taught that they must change their actions and even stop sinning in order to be saved, but, on the contrary, faith (in our minds) is the only requirement for salvation (John 3: 16); i.e. just accepting God’s grace (Ephesians 2:8-10). In other words, some people teach that one needs to first clean up his life, and then he can be saved. However, it’s the other way around: First he just accepts (in his mind) what God has already done to cover his sins through Christ’s death on the cross, and then (once saved) he has the power of the Holy Spirit to overcome sin (in his actions). However, we must also remember that 1 John 1:8 tells us that believers continue to sin, because the flesh (the old sin nature) is not removed at salvation, and we will never become perfectly sinless in this life.