The summing up of Our Lord’s teaching is that the relationship which He demands is an impossible one unless He has done a supernatural work in us. Jesus Christ demands that there be not the slightest trace of resentment even suppressed in the heart of a disciple when he meets with tyranny and injustice. No enthusiasm will ever stand the strain that Jesus Christ will put upon His worker, only one thing will, and that is a personal relationship to Himself which has gone through the mill of His spring-cleaning until there is only one purpose left – I am here for God to send me where He will. Every other thing may get fogged, but this relationship to Jesus Christ must never be.
The Sermon on the Mount is not an ideal, it is a statement of what will happen in me when Jesus Christ has altered my disposition and put in a disposition like His own. Jesus Christ is the only One Who can fulfil the Sermon on the Mount.
If we are to be disciples of Jesus, we must be made disciples supernaturally; as long as we have the dead set purpose of being disciples we may be sure we are not. "I have chosen you." That is the way the grace of God begins. It is a constraint we cannot get away from; we can disobey it, but we cannot generate it. The drawing is done by the supernatural grace of God, and we never can trace where His work begins. Our Lord’s making of a disciple is supernatural. He does not build on any natural capacity at all. God does not ask us to do the things that are easy to us naturally; He only asks us to do the things we are perfectly fitted to do by His grace, and the cross will come along that line always.