There was a scholar of the law who stood up to test him and said, "Teacher, what must I do to inherit eternal life?" Jesus said to him, "What is written in the law? How do you read it?" He said in reply, "You shall love the Lord, your God, with all your heart, with all your being, with all your strength, and with all your mind, and your neighbor as yourself." He replied to him, "You have answered correctly; do this and you will live." But because he wished to justify himself, he said to Jesus, "And who is my neighbor?" Jesus replied, "A man fell victim to robbers as he went down from Jerusalem to Jericho. They stripped and beat him and went off leaving him half-dead…
He answered, "The one who treated him with mercy." Jesus said to him, "Go and do likewise." (Lk 10:25-37)
Scholar of the law knew the demands of the law. He had the intellectual knowledge of it and he was right at that. He knew what eternal life was. And he also knew how to inherit the eternal life. He wanted to justify himself. His knowledge and his questioning and his explanations were all for justification only. In this parable Jesus indirectly says that self-justification does not lead anyone anywhere.
Jesus expectation was that knowledge should lead to action. He said: "You have answered correctly; do this and you will live." Love should be shown in action. Theoretical love does not help. Love of the neighbor should be shown in action. In the parable there were people who justified their action of liturgy and cult. They were justified in going ahead with their works but they did not have love for their neighbor.
Neighbor is the one who was most in need. The one who was suffering was the neighbor in this parable. Samaritan inherits eternal life in this parable because he took care of the one who was most in need and the one who suffered most; and he took care of him to the very end. He helped him until he got cured completely.
