Dr. Martin Luther designed this seal while teaching at Wittenberg. He wanted it to summarize his faith. Here is Luther’s own description of his seal:
The first thing expressed in my seal is a cross, black, within the red heart, to put me in mind that faith in Christ crucified saves us. “For with the heart man believes unto righteousness.” Now although the cross is black, shameful, and intended to cause pain yet it does not change the color of the heart, does not destroy nature. In other words, it does not kill but keeps alive. “For the just shall live by faith” — by faith in the Savior. But this heart is fixed on the center of a white rose to show that faith causes joy, comfort, and peace. The rose is white, not red, because white is the ideal color of all angels and blessed spirits. This rose, moreover, is fixed in a sky-colored background, to show that such joy of faith in the spirit is but a promise and beginning of heavenly joy to come. This joy, though not yet revealed, is looked forward to and held by the hope which we have. Around this background is a ring, to show that such bliss in heaven is endless. And since the ring is made of gold, the best and most precious metal, it also shows that the bliss of heaven is more precious than all other joys and treasures.
(Quoted from Martin Luther: Hero of Faith, by Frederick Nohl, CPH 1962, pp. 148-49.)