The disciples went out and were preaching that people should repent.
The main substance of the disciples’ preaching was the call to repentance. This was the same message that had been proclaimed in the ministry of John the Baptist (Mark 1:4) and later in the ministry of Christ (Mark 1:15). Entrance into the kingdom of God begins with the turning of the heart, and without repentance a person cannot truly receive the Gospel, because he does not recognize his sin and his need for God. The disciples do not address people with pleasing words, but call them to repentance—to leave sin and change their course. Thus it becomes clear that the preaching of the Gospel always has a definite demand: it is not only a promise, but also a call to bring a person’s life into harmony with the will of God.