Charles Spurgeon Commentary Matthew 9:12-13

"But when he heard it, he said, They that are whole have no need of a physician, but they that are sick. But go ye and learn what [this] meaneth, I desire mercy, and not sacrifice, for I came not to call the righteous, but sinners." — Matthew 9:12-13 (ASV)

But when Jesus heard that, he said unto them, They that be whole need not a physician, but they that are sick. But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance.

If he had come to call the righteous, where would he have found them? His call was not likely to be heeded by the self-righteous, but sinners heard it with joy, and so were made righteous by him.