In 1521 the emperor of Germany placed Martin Luther under the ban for preaching the Gospel. In order to protect Luther the elector of Saxony, Fredrick the Wise, disguised him as a knight and hid him at Wartburg Castle (where he translated the New Testament into German). As part of the disguise Luther was given the above coat of arms. That coat of arms is a symbolic portrayal of the Gospel message. The symbolism is this:

When Christ, who took my sins upon Himself on the cross (the black cross), dwells in my sinful heart (the red heart), then I dwell in Christ and am clothed in His righteousness (the white rose), and heaven (the blue background) and eternal life (the gold ring) is mine through faith in Him.