As Jesus was going down the road, he saw Matthew sitting at his tax-collection booth. "Come, be my disciple," Jesus said to him. So Matthew got up and followed him.
That night Matthew invited Jesus and his disciples to be his dinner guests, along with his fellow tax collectors and many other notorious sinners.
The Pharisees were indignant. "Why does your teacher eat with such scum?" they asked his disciples.
References for Matthew 9:11
When he heard this, Jesus replied, "Healthy people don't need a doctor -- sick people do."
Then he added, "Now go and learn the meaning of this Scripture: 'I want you to be merciful; I don't want your sacrifices.' For I have come to call sinners, not those who think they are already good enough."
References for Matthew 9:13