What does Luke 12:18 mean?

A man in a large crowd shouted out for Jesus to settle an inheritance dispute. Jesus responds by telling the crowd a parable about a rich man who, thanks to a good harvest, has become even wealthier. He now needs to decide what to do with his grain. He could give it to the needy (Proverbs 11:26). He could sell it and give the money to the temple to support the priests. Or he could use the money to benefit his community, like building a synagogue (Luke 7:2–5). He might have done any number of things that would have followed God's plan. He does none of these things.

His heart is filled with covetousness: with greed and selfishness. He has much, but he wants more. So, he decides to build bigger barns, store the bounty, and live a life of leisure. He doesn't understand that he will lose his life this night. All those riches will mean less than nothing since they distracted him from seeking the riches of God's grace (Luke 12:13–21).

This view resembles Isaiah 22:12–13 where the Israelites celebrated when they should have mourned. Both reflect Ecclesiastes 9:1–10, written from the point of view of someone who only keeps in mind his earthly life. The man in Ecclesiastes knows that death will come to all, whether they are righteous, unrighteous, wise, or foolish. He decides it's best to work hard, enjoy one's blessings, and not worry about what will happen after death.

Here, specifically, Jesus is warning the brother and the crowd that wealth can distract them from reconciling with God. After teaching the disciples a bit more, He will return to the theme, warning that lifespans are uncertain and the time to repent may be short (Luke 13:1–9). But Jesus also says something about the personal relationship the brother is neglecting. He should seek to reconcile with those he is at odds with—in this case his brother—before seeking justice from an outside party. The verdict may not go his way, and he may find himself bankrupt and in prison (Luke 12:57–59).