The question Jesus never answers is what is the one thing. He tell him he is lacking one thing. He tells him that in order to acquire the one thing he needs to sell what he has, but he never names the one thing he is lacking.
Perhaps this is good, because it creates a space for us to fill. What is the one thing that we are lacking? What is it that keeps us from following Jesus completely? Jesus, "having looked at him, loved him" and he saw what was missing and what this particular man needed to do to fill the void properly.
Are we willing to hear the voice of Jesus, acknowledge what we are lacking, and do whatever Jesus calls us to do, or are we like the young man in the story, too wedded to our stuff, to our current way of life.
Today let us open our hearts acknowledge what we lack, and listen for the voice of Jesus.