Dear Theresa:

This quote is cited in the 1922 book, Rebuilding a Lost Faith by John Stoddard. This book is about Stoddard's 40 year search for truth going from a Protestant seminarian to an agnostic to a Catholic (late in life).

I also found a comment on the website of the Wisconsin Evangelical Synod admitting to this quote from Luther and making this comment about it:

It's too bad that Luther seems to imply that he has the right to add the word alone if he chooses to do so. It would have been better if he had answered by saying that the Greek text indicates that the idea of "alone" though not stated explicitly is implicit in the words Paul used.

In verse 27 Paul says that boasting about anything I contribute to my salvation is totally excluded (emphasis on "totally" which is expressed by the prefix ex- on the Greek verb). Then in verse 28 Paul says that a person is justified (acquitted) totally apart from anything he does to keep God's law (emphasis again on "totally" which is expressed by the Greek preposition choris which means "completely apart from"). So one could translate the meaning of the Greek by saying "a person is acquitted by faith totally apart from doing what God requires in the law" or one could translate "a person is acquitted by faith alone apart from doing what God requires in the law". Either translation would bring out the emphasis of the original Greek text. This would have been a better answer on Luther's part.

Lutherans don't accept every interpretation Luther wrote, nor do they defend everything he says. Rather, Lutherans thank God that through Luther he restored to the church the only proper way of interpreting the Scripture, namely, letting Scripture interpret Scripture (instead of tradition or reason - or Luther - being the final arbiter of meaning).

God Bless,
Bro. Ignatius Mary