The meaning of the word repentance has been twisted in recent years to the point that its biblical meaning is now obscured in the minds of many. The idea that genuine repentance could result in anything but a change of life is completely foreign to Scripture.
What does the Bible teach about the relationship between salvation and repentance? First, it teaches that repentance is essential to salvation. One cannot truly believe unless he repents, and one cannot truly repent unless he believes. Repentance and faith are two sides of the same coin (but they are not synonymous terms). Acts 11:18 and 2 Peter 3:9 are two of the many verses that teach that repentance is necessary for salvation. Perhaps 2 Timothy 2:25 best sums up the relationship between repentance and saving faith when it speaks of "repentance to the acknowledging of the truth" (see also Acts 20:21).
Second, the Greek word for repentance (metanoia) means "to have another mind," but it cannot properly be defined to exclude a sense of hatred of and penitence for sin. The biblical concept of repentance involves far more than merely a casual change of thinking. Biblically, a person who repents does not continue willfully in sin. Repentance is a turning from sin, and it always results in changed behavior (Luke 3:8). While sorrow from sin is not equivalent to repentance, it is certainly an element of scriptural repentance (2 Corinthians 7:10).
Finally, despite what is being widely taught today, affirming that repentance and acknowledgement of Jesus' lordship are necessary to salvation does not "add" anything to the requirement of faith for salvation. It is not "faith plus repentance" that saves, but rather a repentant faith. The notion that salvation is possible apart from a genuine, heartfelt repentance, which includes a deep hatred of sin, is a relatively new one, neither believed nor taught by the people of God until the twentieth century.