Hi James. I thought you might be interested in attempting to track down the following alleged Luther quote in its context: "We must concede to the Papists that we have no knowledge of the scriptures apart from them."This quote is probably a version of something I tracked down many years ago (2006). It was the main subject of this blog entry: Luther: The Infallible Church Declared The Contents of Scripture? If it's the same quote, it's usually cited as "We are obliged to yield many things to the Papists--that with them is the Word of God, which we received from them; otherwise we should have known nothing at all about it."
The citation is from Luther’s Sermons on John 16 [LW 24] (not a commentary, as is often asserted by Roman Catholics using the quote). Luther preached on John 14-16 after March 14, 1537, finishing in either June or July of 1537. The sermons were taken down and edited by Caspar Cruciger. Luther actually credits Cruciger for writing the book. In other words, Luther didn’t sit down and write an exegetical commentary on John. Rather, this quote was the result of preaching, and someone else writing it down the way he heard it.
In my old entry on this quote I've presented the context, so there's no need to re-post it all again. Is Luther conceding an infallible church gave us the canon? Absolutely not. Is Luther saying an infallible extra-biblical tradition produced the Canon? No. Luther is simply saying that he learned about the Scriptures, Baptism, and the Pulpit, etc. from the church of his day, in the same way the Prophets were born into a society in which the religious structure of their day was functioning, and gave the Old Testament people a religious context to live in.