The question was a good one, but the motive was not. Luke says the lawyer "tempted him," meaning he put Jesus to the test. Barnes says he "Feigned a desire to be instructed," but asked in order to perplex Jesus, "or to lead him, if possible, to contradict some of the maxims of the law." Gill says he wanted to see whether Jesus would say anything contrary to the law, "and see if he could gain any advantage against him."

Gill notes it was "the same question as was put by the young ruler" (Mark 10:17), and says both men were "seeking eternal life by their own works." Matthew Henry warns, "If we speak of eternal life, and the way to it, in a careless manner, we take the name of God in vain."

Jesus answered with two questions of His own: "What is written in the law? how readest thou?" (Luke 10:26). The lawyer replied with the law's two great commands, to love God with all the heart, soul, strength, and mind, "and thy neighbour as thyself" (Luke 10:27). Jesus said, "Thou hast answered right: this do, and thou shalt live" (Luke 10:28). But the lawyer, "willing to justify himself," asked, "And who is my neighbour?" (Luke 10:29), and Jesus answered with the parable of the good Samaritan (Luke 10:30-37).

Barnes describes a lawyer as "One who professed to be well skilled in the laws of Moses, and whose business it was to explain them." The Greek for "tempted" is ekpeirazon, to test or try. "What shall I do" uses poiesas, "having done."

The lawyer's answer in Luke 10:27 joins two Old Testament commands: love the LORD "with all thine heart, and with all thy soul, and with all thy might" (Deuteronomy 6:5) and "love thy neighbour as thyself" (Leviticus 19:18). Barnes says Jesus "referred him to the 'law' as a safe rule."

Jesus took a trap and turned it into a mirror. Instead of debating, He sent the lawyer back to the Scriptures he already knew, and let them speak. The law's answer was right, but it was also searching: love God with everything, and love your neighbor as yourself. The lawyer's next question shows he was "willing to justify himself" (Luke 10:29).

The same question comes up again later in Luke, from a rich ruler: "Good Master, what shall I do to inherit eternal life?" (Luke 18:18). Both times Jesus pointed the man back to the commandments he already knew (Luke 10:26; Luke 18:20). Just before this, Jesus had thanked the Father for revealing these things "unto babes" and hiding them "from the wise and prudent" (Luke 10:21). The expert in the law stood up to test Jesus, yet he was the one being tested.