Christ's Death Earns a Complete Salvation
By departing with the word "it is finished," Christ indicates that all Scripture is fulfilled. He says in effect: World and devil have done as much to Me as they were able to do, and I have suffered as much as was necessary for the salvation of men and as was prophesied and proclaimed in Scripture through the prophets. Therefore everything is fulflled and finished. We are to mark this well: Christ's suffering is the fulfilling of Scripture and the redemption of the human race. It is finished! God's Lamb is slaughtered and sacrificed for the world's sin. Sin is wiped out, God wrath is appeased, death is overcome, the kingdom of heaven is won, and heaven is unlocked. Everything is fulfilled and finished, and no one need argue that something still remains to be fulfilled and perfected.
(What Luther Says - para - #566).