It is Augustine who gave us the Reformation. For the Reformation, inwardly considered, was just the ultimate triumph of Augustine's doctrine of grace over Augustine's doctrine of the Church. The doctrine of grace came from Augustine's hands in its positive outline completely formulated: sinful man depends for his recovery to good and to God entirely on the free grace of God...
Therefore, when the great revival of religion that we call the Reformation came, seeing that it was, on the theological side, a revival of "Augustinianism"... there was nothing for it but the rending of the Church.
BB Warfield in Calvin and Augustine p. 322 & 323 P&R.