“With Luther, the Reformers saw all Scripture as being, in the last analysis, either law or gospel – meaning by ‘law’ all that exposes our ruin through sin and by ‘gospel’ everything that displays our restoration by grace through faith – and the heart of the biblical gospel was to them God’s free gift of righteousness and justification. Here was the sum and substance of that sola fide – sola gratia – solo Christo – Sola Scriptura – soli Deo gloria which was the sustained theme of their proclamation, polemics, praises and prayers. And to the minds (note well!) proclamation, polemics, praise and prayer belonged together, just as did the five Latin slogans linked above as epitomizing their message.”
J. I. Packer, “The Reformed Doctrine of Justification” in Soli Deo Gloria, p 11-12