Luther describes the forgiveness won by Christ’s atoning sacrifice like “a chest full of gold and great treasure buried or preserved in a certain place.”

He says, “I might think myself to death and experience all desire, great passion and ardor in such knowledge and remembrance of the treasure until I became ill. But what benefit would all this be to me if this treasure were not opened, given and brought to me and placed in my keeping?”

He further explains: “So that our readers may the better perceive our teaching, I shall clearly and broadly describe it. We treat of the forgiveness of sins in two ways. First, how it is achieved and won. Second, how it is distributed and given to us. Christ has achieved it on the cross, it is true. But He has not distributed or given it on the cross. He has not won it in the Supper or Sacrament. There He has distributed and given it through the Word, as also in the Gospel, where it is preached. He has won it once for all on the cross. But the distribution takes place continuously, before and after, from the beginning to the end of the world. For inasmuch as He had determined once to achieve it, it made no difference to Him whether He distributed it before or after, through His Word, as can easily be proved from Scripture….” [Cf. Rom. 3:21-26; 2 Cor. 5:18-21.]

“If now I seek the forgiveness of sins, I do not run to the cross, for I will not find it given there. Nor must I hold to the suffering of Christ, as Dr. Karlstadt trifles, in knowledge or remembrance, for I will not find it there either. But I will find in the Sacrament or Gospel the Word which distributes, presents, offers and gives to me that forgiveness which was won on the cross.”

“Against the Heavenly Prophets,” LW, 40, 212-213