Aside from justification, the law and gospel distinction must be understood

"Now, of all doctrines the foremost and most important is the doctrine of justification. However, immediately following upon it, as second in importance, is this, how Law and Gospel are to be divided. The distinction between the Law and the Gospel shall now claim our attention and form the subject of our earnest study." -C. F. W. Walther, The Proper distinction between Law and Gospel, Pg. 5