Man's failure is not due to his weakness, but to his not accepting God's strength. It is not in his inability but in not allowing God to enable him. He cannot do it, but why not let God deliver him? This is what the Lord stresses here. The things which are impossible with men are possible with God. Our Lord wanted to prove to the young ruler what God can do, but he, instead, went away with the conclusion that the thing was impossible to him.