Mat 9:12 Those who are whole do not need a physician, but those who are sick.

The word translated "are" is echo, which means "to have."
The word translated as "whole" is ischuo, which means "to be strong," "to be able," or "to have powerful."
The word translated as "physician" is iatros, which means "healer," "medic," or "physician."
The word translated as "sick" is kakos, which means many different forms of "bad," including "ugly," "low born," "craven," "evil," and "ill." It is from the same root as kakia, which, as we have said before, is much closer in sense to our idea of "evil" (and is translated that way in the Bible) than poneros, the most common word translated as evil in the NT, but which means "oppressed by toil."

Another version: Those who have power have no need of a healer but those who have weaknesses.

The larger sense of what Christ is saying is that he didn't come for the strong and powerful. He came to heal to the bad, low-born, and sick. I think he is also hinting the people are ever not as strong and powerful as they think. We are all in need of healing. This fits perfectly with Christ's larger message, that his goal is the perfection of humanity.