Here are two great quotes from Martin Luther.

“Christians cannot be ruled by any other means than the Word of God. For Christians must be ruled in faith, not by outward works. Faith, however, can come through no word of man, but only through the Word of God, as Paul says Romans 10:17 ‘Faith comes by hearing, and hearing by the Word of Christ.”

“If I profess with the loudest voice and clearest exposition every portion of the truth of God, except precisely that little point at which the world and the devil are at that moment attacking, I am not confessing Christ, however boldly I may be professing Him. Where the battle rages, there the loyalty of the soldier is proved; and to be steady on all battlefields besides is mere flight and disgrace if he flinches at that point.”