Mark 2:17

And when Jesus heard it, he saith unto them, They that are whole have no need of a physician, but they that are sick: I came not to call the righteous, but sinners.

Jesus' reply was undisguised irony. That assemblage in Matthew's house knew the Pharisees for what they were, proud, arrogant, unscrupulous, hypocritical, ruthless, and thoroughly wicked sons of the devil. Matthew himself was called of God to outline the character of those men in his gospel in order that all future generations would know WHAT KIND OF MEN engineered the chosen people's rejection of their Messiah.

They that are sick ... Indeed, the Pharisees were the sickest people in Jerusalem; and the Lord's suggestion that "the whole" needed no physician must have been greeted with a gale of laughter. Self-righteousness received its justly deserved rebuke.

I came not to call the righteous, but sinners ... Our Lord's mission was to redeem men from sin, and ever prerequisite to that redemption is the consciousness of the sinner that he needs it, that he is condemned, lost, out of fellowship with the Eternal, and utterly unable to merit anything other than the penalty of death due to sin, and that in Jesus Christ alone has man's sufficient sacrifice appeared. In him alone is the hope of cleansing, pardon, and eternal life. Alas, the Pharisees and their associates were never able to see it. Their sins were known to all except themselves; and they were too proud to learn from Jesus.