"Now after that John was put in prison, Jesus came into Galilee, preaching the gospel of the kingdom of God, And saying, The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel." (Mark 1:14, 15)
There are many passages in the New Testament which indicate that repentance is the key to salvation. For example, Paul said that he had preached everywhere that they "should repent and turn to God, and do works meet for repentance" (Acts 26:20). But he also preached that faith in Christ is the way to be saved. "Believe on the Lord Jesus Christ, and thou shalt be saved" (Acts 16:31). One could cite many verses stressing repentance and many that stress faith.
There can obviously be no real conflict here, though there is a danger in what has been called "easy believism," if repentance is ignored. Mental assent to certain facts about Christ is not true saving faith. Nor will it produce salvation for a person merely to be sorry for his sins and change his behavior if he did not really trust from his heart in the person and work of Christ.
It is not "either/or" but "both/and." One cannot truly repent (that is "change his mind" about Christ and His work, as well as his own life) without genuinely believing personally that Christ died for his sins and rose again to provide his salvation. Neither can one have genuine faith in Christ as Son of God and as his own personal Savior without having his whole life and attitude changed.
It is like two sides of the same coin--repentance on one side, faith on the other. We can only see one side at a time, but both are real and neither can be there without the other. The real "formula" for salvation is "repentance toward God, and faith toward our Lord Jesus Christ" (Acts 20:21). As Christ Himself preached (see our text): "Repent ye, and believe the gospel." HMM