Daily Luther: A Christian Only Has One Foot in the Grave.
A Christian has already been thrust into death by the very fact that he became a Christian. Wherever he may be, he occupies himself with this hourly. He expects death any moment so long as he sojourns here, because devil, world, and his own flesh give him no rest. However, he enjoys the advantage of already being out of the grave with his right leg. Moreover, he has a mighty helper who holds out His hand to him, namely, His Lord Christ; He has left the grave entirely a long time ago, and now He takes the Christian by the hand and pulls him more than halfway out of the grave; only the left foot remains in it. For his sin is already remitted and expunged, God’s wrath and hell are extinguished, and he already lives fully in and with Christ with regard to his best part, which is the soul, as he partakes of eternal life. Therefore death can no longer hold him or harm him. Only the remnant, the old skin, flesh and blood, must still decay before it, too, can be renewed and follow the soul. As for the rest, we have already penetrated all the way into life, since Christ and my soul are no longer in death.
Martin Luther, Luther’s Works, Vol. 28: 1 Corinthians 7, 1 Corinthians 15, Lectures on 1 Timothy, ed. Jaroslav Jan Pelikan, Hilton C. Oswald and Helmut T. Lehmann, 1 Co 15:26–27 (Saint Louis: Concordia Publishing House, 1999).