When does it start?

The question that confronts any serious reading of the Sermon on the Mount is this: Would Jesus have seen a difference between a kingdom ethic for his followers in their so-called private life but a different ethic in public? I doubt it. Why? Because Jesus’ Messianic Ethic, an ethic for his community of followers, is an Ethic from Above and Beyond. The question every reader of the Sermon must ask is this: Does that world begin now, or does it begin now in private but not in public, or does it begin now for his followers in both private and to the degree possible in the public realm as well?— Sermon on the Mount, page 129