"Jesus...is the one whom God exalted to His right hand as a prince and a savior, to grant repentance to Israel, and forgiveness of sins." Peter, Acts 5:30-31.
The Bible teaches that repentance is a gift from God.
In this passage, Peter says to the Sanhedrin that God placed Jesus at His right hand in order to grant repentance to Israel. In other words, Jesus does not only grant the result of repentance (God's forgiveness of sins), but the repentance itself, the change of heart which secures the blessing.
This truth is supported elsewhere in Scripture. In Acts 11:18, the Jerusalem elders realized from Cornelius' conversion that God had granted repentance to Gentiles. God didn't just granting eternal life to Cornelius, or the opportunity to repent, but the repentance that leads to life. They knew wiuth certainty God had granted this gift to Cornelius, ipso facto because Cornelius had repented.
Hebrews 6:6 says that spiritual renewal is unto repentance. Sinners need God's renewing work on their hearts, because their souls are spiritually dead. God only renews a sinner to saving repentance one time. Repentance doesn't cause inner renewal. Inner renewal causes repentance.
In 2 Timothy 2:25, Paul counsels gentleness toward unbelievers, in case God grants them repentance. The context presumes that the gift of repentance will change their argumentative attitude.
The same truth is taught regarding faith, which is the conjoined-twin to repentance, Christ told a crowd that they could not believe in Him apart from divine drawing (John 6:44). He repeats this in 6:65, saying strongly that no one can believe in Him unless God grants it. Because the human heart is spiritually enslaved by sin and Satan, human beings have no natural capacity for saving faith. Pre-conversion grace can't "stimulate" a latent positive response to the Gospel, because there's nothing alive in there to stimulate. It would be like poking a corpse with a stick.
Jesus further said that God's gift of faith is always successful. He said that everyone to whom God gives the gift of faith comes to Him (6:45), and as a result none of them can be eternally lost (6:39-40). Since your saving faith did not originate with you, you do not control it, and you cannot expel it.
Paul says the same in Ephesians 2:8-9. Even though the pronoun "that" doesn't specifically refer to the word "faith" (since the grammatical gender of "faith" is feminine and "that" is neuter), "that" refers to the entire preceding clause, "by grace you have been saved through faith".
The whole salvation bundle is a gift.
This is an important truth to know, because it keeps us from evangelistic self-reliance and manipulation, and it promotes evangelistic praise. We realize that we absolutely cannot force anyone to believe in Christ. We cannot using natural psychology to drive a true conversion.
We, in our witnessing, are totally dependent on God. By knowing this we will be more ethical, and avoid pushing people's emotional buttons, or confuse their cheers or tears with new birth.
We also give thanks, never to ourselves but only to God, for every person who truly comes to Christ. This truth also provokes prayer for non-Christians, since only individual divine intervention can bring a sinner to repentance.
Every lost person ought to repent, because it's God's will that they should. Sin is always wrong, and obedience is God s always right, regardless of how spiritually unwilling a lost person is. God will use the impenitent to glorify Himself on the day of their judgment (Proverbs 16:4). We preach to all, without discrimination, that each one should repent and turn to Christ. But God must give the gift of repentance, for their heart-attitudes toward sin and God to change.