Ideas about the Kingdom of the Heavens around us and the unity of believers in Christ within it
When Jesus unfavorably compared the unrepentance of the Galilean towns where he had preached to the repentance Tyre, Sidon and Sodom would have shown to the same preaching. the repentance of which he spoke clearly included behavioral change.
Jesus contrasted the Jewish leaders, who refused to hear his words, with the Ninevites who repented at the preaching of Jonah and put away their bloodshed and violence.
As the parable of the two sons in Matthew 21:28-32 shows, repentance is merely changing our minds so that we start to do what the Father asks. Repentance does not require remorse, payment of a penalty, or even in all cases a spoken apology, and the forgiveness that it produces cannot be sold.
Salvation cannot happen without repentance. But this repentance isn’t remorse, it is changing my mind, turning from my own works and my other idols and turning to the true God. It is never really present without a change in the way I live. But my new way of life does not come from me, but from God who has prepared it for me and lives it through me.
Both John the Baptist and Jesus preached that repentance is required now, because God’s kingdom is now all around us. But the focus of that required repentance was right treatment of each other, not religious works.