Luther came to understand justification as entirely the work of God. When God's righteousness is mentioned in the gospel, it is God's action of declaring righteous the unrighteous sinner who has faith in Jesus Christ. The righteousness by which the person is justified (declared righteous) is not his own (theologically, "proper" righteousness) but that of another, Christ, ("alien" righteousness). "That is why faith alone makes someone just and fulfills the law", said Luther. "Faith is that which brings the Holy Spirit through the merits of Christ". Thus faith, for Luther, is a gift from God, and ". . .a living, bold trust in God's grace, so certain of God's favor that it would risk death a thousand times trusting in it." This faith grasps Christ's righteousness and appropriates it for the believer. He explained his concept of "justification" in the Smalcald Articles: