I answer, not only in the beginning of our conversion, but also in the continuance and final accomplishment thereof. For here Paul desires in the day of judgment to stand before God only by the justice of faith without his own justice of the law. And Paul brings in Abraham (as I have noted before) in the very midst of godly conversation and holy obedience to be justified without any works by his faith in the Messiah [Rom. 4:2–3]. And Paul avouches three things of faith:
(1) by it ‘we have access’ to the grace of God;
(2) by it we ‘stand in the same grace’;
(3) by it ‘we rejoice under the hope of glory’ [Rom. 5:2].
Thus then, we see there is only one way of justification, namely that we are justified and accepted of God to life eternal through grace alone by faith alone for Christ alone in the beginning, middle, and end of our conversion. And here is plainly discovered the error of the Church of Rome. It makes a double justification: the first [is] whereby the sinner is made of an evil man a just man, and this (they say) is by faith alone; [and] the second is whereby a man of a just man is made more just, and this (they say) is by faith and works together. But [they speak] falsely.
William Perkins, The Works of William Perkins, 9:65–66. (HT: Inwoo Lee)