Martin Luther's protest of salvation by the works of the Catholic Church was the cause of his contending for salvation by faith only . The Protestants were wrong when they implied that merely by believing certain propositions we would be justified before God, and the Catholics were wrong when they said that simply by obeying the commandments we would be just. Neither is sufficient . True faith in God requires a personal response to God. This response involves a personal reliance on God, a trust that is exhibited in how one lives.
Works prove the character of our faith.
Just as important as what you do, is why you do it. He had no evidence of a new life, no saving faith. It has been said that justice is giving a person what they deserve, mercy is not giving them what they deserve, and grace is giving them what they don't deserve. Because we sin daily, we don't deserve to get to heaven, but through faith in Jesus Christ, we will be given the eternal life we neither deserve nor earn. They tremble, not out of reverence, but hatred and opposition to God, on whom they believe.