You might hear liberal pastors and laypeople talk about interpreting the meaning of the Confessions by using the Scriptures. This is ALWAYS a tip-off to foul play -- and the discerning Lutheran should be ready to call it into question.
Commenting on the subject as to whether we should interpret the Confessions in light of the Scriptures, C.F.W. Walther wrote:
“Some want to subscribe to the Symbols with the proviso that they may interpret them according to Scripture or understand them correctly. This was the condition under which the Reformed declared themselves ready to subscribe to the Unaltered Augsburg Confession.” (Why Should Our Pastors, Teachers and Professors Subscribe Unconditionally to the Symbolical Writings of Our Church)
Likewise we read in Pieper's Christian Dogmatics, some further detail about this subject (vol. 1, pp. 354ff.), describing a quatenus subscription in its varied forms, including the position of those who say that the Confessions are to be interpreted by Scripture:
“Again, there are those who are ready to subscribe to the Confessions with the understanding that they be interpreted ‘according to Scripture,’ or ‘correctly.’ . . . By subscribing to the Symbols a man does not declare his readiness to interpret them ‘according to Scripture,’ but the minister or candidate in question makes the solemn declaration to the congregation that he has already discovered what Scripture teaches and he finds the Lutheran Confessions to be the expression of his own faith and confession.”
We don't use the Scriptures to interpret the Confessions. We use the Confessions to interpret the Scripture BECAUSE the Confessions ARE the true and accurate exposition of God's Word in Law and Gospel. Confessional Lutherans have a quia (literally, "because") subscription to the Confessions rather than a quatenus (literally, "in so far as") subscription.
When anyone suggests that they want to do things the other way around, they are likely putting a spin not only on the Confessions, but also on the Scriptures.