Jesus now points the questioner to the familiar commandments of the second table of the law. It is precisely in showing charity that our love for God is revealed. Our actions (note the what must I do?
in the question in Luke 18:18!) reveal that we are keeping God's commandments.
20 You know the commandments: ‘Do not commit adultery, Do not murder, Do not steal, Do not bear false witness, Honor your father and mother.’”