Mark 2:16

When Jesus is attacked for mixing with sinners, and taking as his disciple a despised tax collector, one might ask: What could he possibly gain by doing so? Only the salvation of sinners. To blame Jesus for mingling with sinners would be like blaming a physician for stooping down over suffering and putting up with vile smells in order to heal the sick.

(ubi sup.) If by the election of Matthew and calling of the publicans, the faith of the Gentiles is expressed, who formerly were intent on the gains of this world; certainly the haughtiness of the Scribes and Pharisees intimates the envy of the Jewish people, who are vexed at the salvation of the Gentiles. It goes on: When Jesus heard it, he saith unto them, They that are whole need not the physician, but they that are sick. He aims at the Scribes and Pharisees, who, thinking themselves righteous, refused to keep company with sinners. He calls Himself the physician, Who, by a strange mode of healing, was wounded on account of our iniquities, and by His wound we are healed. And He calls those whole and righteous, who, wishing to establish their own righteousness, are not subject to the righteousness of God. Moreover He calls those rich and sinners, who, overcome by the consciousness of their own frailty, and seeing that they cannot be justified by the Law, submit their necks to the grace of Christ by repentance. Wherefore it is added, For I came not to call the righteous, but sinners, &c.

And the scribes and Pharisees seeing that he was eating with sinners, etc. If through Matthew's choosing and calling the faith of the publicans is expressed of the gentiles, who first coveted the gain of the world, but now are refreshed with the Lord at the feast of charity and with diligent devotion of good works, surely the pride of the scribes and Pharisees indicates the envy of the Jews, troubled about the salvation of the gentiles. He speaks to them: Amen I say to you, that the publicans and prostitutes will precede you into the kingdom of God.—Hearing this Jesus said to them: The healthy do not need a physician, but those who are ill. For I did not come to call the righteous but sinners. He reproaches the scribes and Pharisees, who, thinking themselves righteous, shunned the company of sinners. He calls himself a physician, who by a marvelous kind of healing was wounded for our iniquities, and by his bruises we are healed (Isaiah 53). Moreover, he calls healthy and righteous those who, ignorant of God's righteousness, and wanting to establish their own, have not subjected themselves to the righteousness of God (Romans 10); who, presuming on the law, do not seek the grace of the Gospel. Furthermore, he calls the ill and sinners those who, overcome by the consciousness of their fragility, and seeing that they cannot be justified by the law, submit their necks to the grace of Christ by repenting.