CFW Walther was the first president of the Lutheran Church-Missouri Synod, first president of Concordia Seminary and a parish pastor to boot! His book, "Law and Gospel" is a classic and one of the first books read by every seminarian.
"Law and Gospel" is comprised of a series of lectures. Right at the outset, Walther shares his goal with his students:
I wish to talk the Christian doctrine into your very hearts...