"On Preaching" from the Confessions (#14)

And when the word “Gospel” is used in its broad sense and apart from the strict distinction of law and Gospel, it is correct to define the word as the proclamation of both repentance and the forgiveness of sins. For John, Christ, and the apostles began in their preaching with repentance and expounded and urged not only the gracious promises of the forgiveness of sins but also the divine law. In addition, however, the word “Gospel” is also used in another (that is, in a strict) sense. Here it does not include the proclamation of repentance but solely the preaching of God’s grace. So it appears shortly afterward in the first chapter of St. Mark, where Christ said, “Repent and believe in the Gospel” (Mark 1:15). (Tappert, The Book of Concord. Fortress Press: Philadelphia, 1959, p.559; FC SD V: 5-6)