What does Mark 10:19 mean?

A man has asked Jesus how he can inherit eternal life, and Jesus responds by listing most of the commandments that have to do with loving others (Exodus 20:12–17). In Matthew, Jesus adds, "You shall love your neighbor as yourself," (Matthew 19:19). In Mark, Jesus adds that the man must not defraud.

"Do not defraud" is not in the Ten Commandments, although the Mosaic law does speak of it. Leviticus 19:35 says, "You shall do no wrong in judgment, in measures of length or weight or quantity. You shall have just balances, just weights, a just ephah, and a just hin." Deuteronomy 25:13–16 also demands that Jews not cheat in their weights and measures, ending with "For all who do such things, all who act dishonestly, are an abomination to the LORD your God." It may be that Jesus uses defrauding as a natural consequence of coveting, the tenth commandment. Because the young man is rich, his temptation towards coveting might have been along the lines of cheating in business deals.

Before the crucifixion, Jesus sent the disciples out to preach the gospel of repentance (Mark 6:12) as John the Baptist did (Mark 1:4). In that kind of direct evangelism, there is no room for the possibility that someone can be good enough to deserve salvation. The gospel is that God forgives, not that we can be perfect. In interactions, however, Jesus is more circumspect. He draws His listeners into the realization that the good works and righteous lives they're so proud of will never be complete. They would have to maim themselves to escape temptation (Mark 9:43–48). Once Jesus' audience realizes they must come to God powerless and without merit, like a child (Mark 10:14), then they will be ready to repent.