A father acts on behalf of his children by working, providing, intervening, struggling, and suffering for them. In so doing, he really stands in their place. He is not an isolated individual, but incorporates the selves of several people in his own self.
When all is said and done, the life of faith is nothing if not an unending struggle of the spirit with every available weapon against the flesh.
Struggling against the legalism of simple obedience, we end by setting up the most dangerous law of all, the law of the world and the law of grace. In our effort to combat legalism we land ourselves in the worst kind of legalism. The only way of overcoming this legalism is by real obedience to Christ when he calls us to follow him; for in Jesus the law is at once fulfilled and cancelled.