Repentance is given to us in scripture as a requirement unto salvation. It is more than simply saying, "I'm sorry". It is the acknowledgement that our lifestyle will forever be altered and that our acceptance of Christ is the most important thing in life. More important especially than the earthly pleasures that we indulged in before our conversion. It is a dedication to keeping our life as pure as we can.

Acts 2:37-38 ? On the day of pentacost, the crowd asks Peter what to do? Part of his answer was to repent.

Acts 3:19 ? Repentance is a required part of forgiveness to have sins removed.

Acts 8:22 ? When Simon the sorcerer tries to purchase the gifts of the Spirit from Peter, Peter tells him to repent of this to be forgiven.

Acts 17:30 ? God commands all men to repent.

Revelation 2:5 ? In speaking to each of the 7 churches, Christ tells those that have problems to repent or risk having their place taken away.