“A Brief Instruction on What to Look For and Expect in the Gospels” – Martin Luther – here is a portion.

At its briefest, the Gospel is a discourse about Christ, that he is the Son of God and became man for us, that he died and was raised, that he has been established as a Lord over all things. This much St. Paul takes in hand and spins out in his epistles. He bypasses all the miracles and incidents [in Christ’s ministry] which are set forth in the four Gospels, yet he includes the whole Gospel adequately and abundantly. This may be seen clearly and well in his greeting to the Romans [1:1-4], where he says what the Gospel is, and declares, “Paul, a servant of Jesus Christ, called to be an apostle, set apart for the Gospel of God which he promised beforehand through his prophets in the holy scriptures, the Gospel concerning his Son, who was descended from David according to the flesh and designated Son of God in power according to the Spirit of holiness by his resurrection from the dead, Jesus Christ our Lord,” etc.

There you have it. The Gospel is a story about Christ, God’s and David’s Son, who died and was raised and is established as Lord. This is the Gospel in a nutshell. Just as there is no more than one Christ, so there is and may be no more than one Gospel….

Yes even the teaching of the prophets, in those places where they speak of Christ, is nothing but the true, pure, and proper Gospel-just as if Luke or Matthew had described it. For the prophets have proclaimed the Gospel and spoken of Christ, as St. Paul here [Rom. 1:2] reports and as everyone indeed knows. Thus when Isaiah in chapter fifty-three says how Christ should die for us and bear our sins, he has written the pure Gospel. And I assure you, if a person fails to grasp this understanding of the Gospel, he will never be able to be illuminated in the Scripture nor will he receive the right foundation.