Luther explained the meaning of the seal in a letter to Lazarus Spengler, a prominent supporter of Luther and a leader of the Protestant Reformation in Nuremberg, on 8 July 1530:
From Dr. Martin Luther at Coburg Castle
Grace and peace in Christ!
Honorable, kind, dear Sir and Friend! Since you ask whether my seal has come our correctly, I shall answer most amiably and tell you of those thoughts which now come to my mind about my seal as a symbol of my theology.
There is first to be a cross, black and placed in a heart, which should be of its natural color, so that I myself would be reminded that faith in the Crucified saves us. For if one believes from the heart he will be justified (Romans 10:10). Even though it is a black cross, which mortifies and which also should hurt us, yet it leaves the heart in its natural color and does not ruin nature; that is, the cross does not kill but keeps man alive. For the just man lives by faith, but by faith in the Crucified One (Romans 1:17). Such a heart is to be in the midst of a white rose, to symbolize that faith gives joy, comfort, and peace; in a word it places the believer into a white joyful rose; for this faith does not give peace and joy as the world gives (John 14:27) and, therefore, the rose is to be white and not red, for white is the color of the spirits and of all the angels (Matthew 28:3, John 20:12). Such a rose is to be in a sky-blue field, symbolizing that such joy in the Spirit and in faith is a beginning of the future heavenly joy; it is already a part of faith, and is grasped through hope, even though not yet manifest. And around this field is a golden ring, symbolizing that in heaven such blessedness lasts forever and has no end, and in addition is precious beyond all joy and goods, just as gold is the most valuable and precious metal.
May Christ, our dear Lord, be with your spirit until the life to come.
- Romans 10:10– For with the heart man believeth unto righteousness; and with the mouth confession is mad unto salvation.
- Romans 1:17– For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
- John 14:27– Peace I leave with you, my peace I give to you: not as the world gives, give I unto you. Let not your heart be troubled, neither let it be afraid.
- Matthew 28:3– His countenance was like lightening, and his raiment white as snow.
- John 20:12– And she beholdeth two angels in white sitting, one at the head, and one at the feet where the body of Jesus had lain.