Jesus stops on one word the ruler used: "good." The ruler meant it as a title of respect, but Jesus wanted him to think about what he was saying. Barnes puts Jesus' meaning this way: "You suppose me to be only a man. Yet you give me an appellation that belongs only to God." Gill says the young man "considered him only as a mere man," and that Jesus meant, from the man's own words, "to instruct him in the knowledge of his proper deity." Matthew Henry hears the question as a challenge: "dost thou then take me for God?" The question presses the ruler on two fronts at once: who is this Jesus he is speaking to, and how good must anyone be to inherit eternal life?

Jesus answers His own question in the same breath: "none is good, save one, that is, God" (Luke 18:19). Then He points the ruler to the law: "Thou knowest the commandments" (Luke 18:20). The ruler does not take up the question of whom he called good. He answers, "All these have I kept from my youth up" (Luke 18:21). Jesus replies, "Yet lackest thou one thing," and calls him to sell all, give to the poor, "and come, follow me" (Luke 18:22). The ruler "was very sorrowful: for he was very rich" (Luke 18:23).

Luke calls the man "a certain ruler" (Luke 18:18). Matthew adds that he was young (Matthew 19:20), and Mark says he came running and kneeled before Jesus (Mark 10:17). The Greek word for "good," agathos, appears twice in this verse: once in the ruler's title for Jesus and once in "none is good." Jesus uses the man's own word.

The commandments Jesus lists in Luke 18:20 come from the Ten Commandments given at Sinai (Exodus 20:12-16), all of them about how a person treats his neighbor. Barnes notes that the ruler had been taught that eternal life was gained by doing good works, which is why he asked what he should "do."

This question sets God Himself as the measure of goodness. Barnes and Gill agree that Jesus was not denying His own goodness, but they read His aim differently. Gill says Jesus meant to lead the ruler to see His deity: if only God is good, then calling Jesus good means more than a polite title. Barnes reads it more narrowly, as a rebuke of using a title that belongs only to God as an empty compliment, and says Christ did not intend here to say anything about His own character. The ruler came asking what he could do. Jesus turned him toward who God is.

The verses that follow carry the point forward. The ruler, who had kept the commandments, still lacked "one thing" and was "very sorrowful" (Luke 18:22-23). Those listening asked, "Who then can be saved?" and Jesus answered that "The things which are impossible with men are possible with God" (Luke 18:26-27). Just before this meeting, Jesus had said the kingdom must be received "as a little child" (Luke 18:17). Eternal life is not earned by being good enough, because only God is good.