The following comes from the book Martin Luther: Selections from his writings edited and with an introduction by John Dillenberger (this is NOT an endorsement of Martin Luther, obviously):
PREFACE TO THE EPISTLES OF ST. JAMES AND ST. JUDE 1
“I think highly of the epistle of James and regard it as valuable although it was rejected in early days. It does not expound human doctrines, but lays much emphasis on God’s law. Yet, to give my own without prejudice to that of anyone else, I do not hold it to be of apostolic authorship, for the following reasons:
Firstly, because, in direct opposition to St. Paul and all the rest of the Bible, it ascribes justifications to works, and declares that Abraham was justified by his works when he offered up his son. St. Paul, on the contrary, in Romans 4[:3], teaches that Abraham was justified without works, by his faith alone, the proof being in Genesis 15:[:6], which was before he sacrificed his son. Although it would be possible to ‘save’ the epistle by a gloss giving a correct explanation of justification here ascribed to works, it is impossible to deny that it does refer Moses’s word in Genesis 15 (which speaks not of Abraham’s works but of his faith, just as Paul makes plain in Romans 4) to Abraham’s works. This defect proves that the epistle is not of apostolic provenance.
Secondly, because, in the whole length of its teaching, not once does it give Christians any instruction or reminder of the passion, resurrection, or spirit of Christ. It mentions Christ once and again, but teachings nothing about Him; it speaks only of a commonplace faith in God. It is the office of a true apostle to preach the passion and resurrection and work of Christ, and to lay down the true ground for this faith, as Christ himself says in John 15 [:27], You shall be my witnesses. All genuinely sacred books are unanimous here, and all preach Christ emphatically. The true touchstone for testing every book is to discover whether it emphasizes the prominence of Christ or not. All Scripture sets forth Christ, Romans 3 [:24 f.] and Paul will know nothing but Christ, 1 Corinthians 2 [:2]. What does not teach Christ is not apostolic, not even if taught by Peter or Paul. On the other hand, what does preach Christ is apostolic, even if Judas, Annas, Pilate, or Herod does it.
The epistle of James, however, only drives you to to the law and its works. He mixes one thing with another to such an extent that I suspect some good and pious man assembled a few things said by disciples of the apostles, and then put them down in black and white; or perhaps the epistle was written by someone else who made notes of a sermon of his. He calls the law a law of freedom, although St. Paul calls it a law of slavery, wrath, death, and sin.
Yet he quotes St. Peter’s saying that ‘Love covers a multitude of sins,’ and again ‘Humble yourselves under the hand of God;’ further, St. Paul’s word in Galatians 5, The spirit lusteth against hate. But St. James was killed by Herod in Jerusalem before St. Peter’s death, which shows the writer to have been far later than St. Peter or St. Paul.
In sum: he wished to guard against those who depended on faith without going on to works, but he had neither the spirit nor the thought nor the eloquence equal to the task. He does violence to the Scripture, and so contradicts Paul and all Scripture. He tries to accomplish by emphasizing law what the apostles bring about by attracting men to love. I therefore refuse him a place among the writers of the true canon of my Bible; but I would not prevent anyone placing him or raising him where he likes, for the epistle contains many excellent passages. One man does not count as a man even in the eyes of the world; how then shall this single and isolated writer count against Paul and all the rest of the Bible?
The Epistle of St. Jude
No one can deny that this epistle is an excerpt from, or copy of, the second epistle of St. Peter, for all he says is nearly the same over again. Moreover, he speaks of the apostles as would a disciple of a much later date. He quotes words and events which are found nowhere in Scripture, and which moved the fathers to reject this epistle from the canon. Moreover, the apostle Jude did not go into Greek-speaking lands, but into Persia; and it is said that he could not write Greek. Hence, although I value the book, yet it is not essential to reckon it among the canonical books that lay the foundation of faith” (Martin Luther, pp. 35-37).
1 Reprinted by permission of the publisher from The Reformation Writings of Martin Luther, volume II, The Spirit of the Protestant Reformation, translated and edited by Bertram Lee Woolf (London: Lutterworth Press, 1956), pp. 306-8).