The Gospel is the power of God unto salvation, but it does not work for everyone! With all of its divine potential, it must have the right soil to germinate and produce a new creation in Christ. The condition of a person's heart determines if  it will take hold. It cannot germinate in a hardened heart anymore than Pharoah's hard heart could obey God's word. Never has this dichotomy been plainer than in the responses of the Two Thieves who died alongside Jesus: One died on the cross of rebellion to enter into eternal damnation, and the other on the cross of repentance entered with Jesus into Paradise.