Final answer:
The author of the New Testament who stressed the importance of works as a demonstration of faith was James. Contrarily, Martin Luther's teachings on salvation emphasized faith alone, inspired by St. Paul's writings, marking a key difference from the Catholic Church's teachings at the time.
Step-by-step explanation:
The New Testament author who emphasized that faith should manifest itself in works was James. This can be seen in the Epistle of James, specifically James 2:14-26 where the relationship between faith and works is explored. While the theologian Martin Luther argued for the doctrine of salvation by faith alone, drawing on the works of St. Paul, who stated, "The just shall live by faith" (Romans 1:17), the Epistle of James offers a different perspective. James argues that faith without works is dead and that works are the evidence of a living faith. The underlying message is that while faith is essential, it should be accompanied by actions that demonstrate that faith.
This concept can be contrasted with the views of the Catholic Church at the time, which taught that good works played a role in one's salvation. This belief included the commission of works of art for the Church as part of these good works. Martin Luther's recognition of human sinfulness and his reading of Paul led to the Protestant Reformation, which held that God's grace is a gift, not something earned by works.