Zacchaeus is a sinful man because he is a chief tax collector and most probably extorts funds from the poor.
Looking into the branches of the tree, Jesus “says to him, ‘Zacchaeus, hurry and come down because today I must stay at your house.'” (Luke 19: 5)
Zacchaeus comes down from the tree, and repents. He speaks of his plans to make restitution. Jesus says, “Today salvation has come to this house.” (Luke 19: 9)
Jesus explains, “For the Son of Man comes to seek and to save the lost.” Jesus promises that He is come to save the sick, not the healthy. He says to the blind man who receives his sight, “Your faith heals you.” (Luke 18: 42) He says to Zacchaeus, you “too are a son of Abraham.” (Luke 19: 9)
When a young rich man who obeys the ten commandments yet will not part with his wealth walks away from salvation, Jesus is asked, “Then who can be saved?” The Lord responds, “What is impossible with men is possible with God.” (Luke 18: 26 – 27)
Jesus’ point is that salvation is not possible for us; it comes only through God. “For the Son of Man comes to seek and save the lost.” Jesus says, “Those who are well don’t need a doctor, but the sick do. Go and learn what this means: I desire mercy and not sacrifice. For I do not come to call the righteous, but sinners.” (Matthew 9: 12 – 13)