God has set things right without laying down a prior condition of any sort. God’s rectifying act, that is to say, is no more God’s response to human faith in Christ than it is God’s response to human observance of the Law. God’s rectification is not God’s response at all. It is the first move; it is God’s initiative, carried out by him in Christ’s faithful death.
J. Louis Martyn on Pistis Christou and Galatians 2:15-21