As Jesus passed on from there, he saw a man called Matthew sitting at the tax office; and he said to him, "Follow me." And he rose and followed him. And as he sat at table in the house, behold, many tax collectors and sinners came and sat down with Jesus and his disciples. And when the Pharisees saw this, they said to his disciples, "Why does your teacher eat with tax collectors and sinners?" But when he heard it, he said, "Those who are well have no need of a physician, but those who are sick. Go and learn what this means, `I desire mercy, and not sacrifice.' For I came not to call the righteous, but sinners."
St. Matthew 9:9-13
Matthew was a Jew who worked for the occupying Roman forces, collecting taxes from other Jews. The Romans didn’t care what the tax collectors got by collecting extra for themselves, and so they were generally hated as traitors by their fellow Jews. The Pharisees lumped them with "sinners.” So it was shocking to them to hear Jesus call such a man to be one of His followers.
Matthew got Jesus in further trouble by having a sort of going-away party at his house. The Gospel tells us that "many" tax collectors and "those known as sinners" came to the dinner. The Pharisees were still more shocked. What business did this supposedly great teacher have associating with such immoral people? Jesus' answer was, "Those who are well do not need a physician, but the sick do. Go and learn the meaning of the words, 'I desire mercy, not sacrifice.' I did not come to call the righteous but sinners.” Jesus is not setting aside ritual and worship; he is saying that it cannot be a substitute for loving others.
When Jesus saw Matthew sitting at his tax office – no doubt counting his day's profit – Jesus spoke only two words – "follow me". Those two words changed Matthew from a self-serving profiteer to a God-serving apostle who would bring the treasures of God's kingdom to the poor and needy. He turned from his sin, so that he could follow Jesus.
O ALMIGHTY God, who by thy blessed Son didst call Matthew from the receipt of custom to be an Apostle and Evangelist; Grant us grace to forsake all covetous desires, and inordinate love of riches, and to follow the same thy Son Jesus Christ, who liveth and reigneth with thee and the Holy Ghost, one God, world without end. Amen.