Martin Luther on Justification by Faith alone in Christ alone

"This is what it means to prevail against the gates of hell: Not to be bodily in an external communion, authority, jurisdiction, or assembly according to your way of babbling about the Roman communion and its unity, but by a firm and true faith to be built upon Christ, the rock which can never be suppressed by any power of the devil, even if he counts more followers and uses unceasing strife, cunning, and violence against it." - Martin Luther, The Papacy in Rome