Jesus Christ set an important pattern in His preaching when He regularly called on hearers to "repent, and believe" (Mark 1:15). The apostle Paul also preached "repentance toward God and faith toward our Lord Jesus Christ" (Acts 20:21).
Repentance—turning back to obeying God after rebelling against Him—begins with crying out to God for forgiveness of our sins and our accepting Jesus Christ as personal Savior. This includes trusting in Christ's sacrifice as bearing the penalty of our sins—believing that by it our repentance is accepted and our sins are forgiven. Repentance is a decision based not on emotion only, though as Acts 2:37 shows, heartfelt emotion is certainly an important part. It is a decision and commitment to sincerely obey God through faith in Jesus Christ. Christ's righteousness becomes ours through faith in and from Him (Philippians 3:8-9; Romans 8:1-4).
This faith is a deep belief and trusting confidence in God (Hebrews 11:1). And we can't come to God without it: "But without faith it is impossible to please Him, for he who comes to God must believe that He is, and that He is a rewarder of those who diligently seek Him" (Hebrews 11:6). Such faith will lead to obeying God. It not only trusts in initial forgiveness of sin, but it recognizes that God will help the faithful to remain faithful.
While repentance involves sorrow over past sins, it includes joy over God's forgiveness and the blessings and future He promises. In Mark 1:15, quoted in part earlier, Jesus specifically called for people to "repent, and believe in the gospel"—referring to the good news of the Kingdom of God. The expectation through faith of being a part of God's Kingdom is certainly reason to rejoice—and it motivates those who take it to heart to do God's will.
After repentance and baptism, God gives His Spirit to us (Acts 2:38). One important result of having the Holy Spirit within us is the development of faith (Galatians 5:22-23; 1 Corinthians 12:4, 9). "The faith of the Son of God" is what we now live by (Galatians 2:20, KJV). Indeed, the just (those who are justified or made right with God) live by faith (Habakkuk 2:4; Romans 1:17; Galatians 3:11; Hebrews 10:38).
The converted person continues through repentance and faith to rely on the sacrifice of Jesus Christ to cover his or her sins in this lifelong process of overcoming. And through the miraculous help of Christ living in him or her through the Holy Spirit, the Christian is able to grow in God's way of life, increasingly walking by faith in obedience to God's law of love (Galatians 2:20; Philippians 4:13; Colossians 1:29).
To learn more about the crucial role of faith in the process of transforming your life, read the free Bible study aid booklet You Can Have Living Faith.