Albert Barnes Commentary Matthew 9:12

"But when he heard it, he said, They that are whole have no need of a physician, but they that are sick." — Matthew 9:12 (ASV)

They that be whole, etc. Jesus, in reply, said that those who are whole did not need a physician. Sick persons only needed his aid. A physician would not commonly be found with those who were in health. His proper place was among the sick.

So, he says, "If you Pharisees are such as you think yourselves, already pure and holy, you do not need my aid. It would be of no use to you, and you would not thank me for it. With those persons who feel that they are sinners I may be useful; and there is my proper place."

Or, the expression may mean, "I came on purpose to save sinners. My business is with them. There are none righteous; and as a physician is in his proper place with the sick, so am I with guilty and miserable sinners."