"The Gospel should predominate" & "Sermons shouldn't end on Law"

The following is a repost of an episode aired on "Christendom and the World". See the link below. In this episode, the Rev. Schlies sit down with Rev. Andrew Preus to discuss the cliche that "The Gospel should predominate in sermons" and "Sermons shouldn't end on the Law". What did C.F.W Walther really mean in Thesis XXV of his lectures on Law and Gospel? How should we think about the form of a sermon?

https://christiannewsmo.libsyn.com/the-schlie-brothers-digging-deeper-than-the-clichs-round-2