What does Matthew 19:20 mean?

The rich, young ruler (Mathew 19:16–19) does not yet understand that he is not good enough to enter the kingdom of heaven and have eternal life. Perhaps, though, he suspects it. He has come asking Jesus for a "good deed" he must do. Jesus has told the man to keep the commandments of Moses and listed five of them. The young man now answers that he has already kept each of these and asks what he still lacks.

The man seems to sense he is still missing something despite following Judaism as closely as he has. He wants Jesus to tell him what key action—or work, or deed—he can do to be guaranteed a place in heaven.

Jesus is about to show the man that he has not kept even these five commands, however. Specifically, the man has not loved his neighbor as he loves himself. He only thinks that he has. The man's idea of human goodness is too small. He is self-deluded.

This question feeds Jesus' ultimate conclusion in the next few verses. That lesson is exactly what Jesus was setting up with His initial response to this man (Matthew 19:17). Salvation comes to those who admit their need and are willing to follow God, regardless of what He asks of them. Those who come to Jesus for salvation by God's grace do so understanding that they are not truly good and need Jesus' goodness instead of their own. Those who insist on their own merits, or won't follow when God's will is unpleasant, are not going to be saved (Matthew 19:21–22).