"Go, now, attack Amalek, and deal with him and all that he has under the ban. Do not spare him, but kill men and women, children and infants, oxen and sheep, camels and asses."
- 1 Samuel 13:3, New American Bible
To be honest, it sounds a lot like the behavior of your typical gaming groups mechanism of dealing with a goblin lair. However, that passage comes straight out of the Bible.
I recently finished Reza Aslan's book Zealot: The Life and Times of Jesus of Nazareth. In it Aslan examines what we know and what we can surmise about the historical figure, Jesus of Nazareth. It's a fascinating work, something I will be reviewing in its own right, either here or in my political blog (or in both places, from different perspectives). I'm pretty certain I'd not want to live in Judea within fifty years of 1 AD. But as a time for adventure, it is an absolutely fascinating period. It is a period of numerous Messiahs who rose up against the Romans in attempts to bring about the Earthly Kingdom of God. It was a time when the people most definitely believed in magic - Aslan pointed out that Jesus the miracle-worker is not something that people of the era would find all that surprising - the shocking thing was he performed these miracles free of charge. The people of the period most certainly believed there were people who could perform miracles.
It is a period of intense resistance to Roman rule, but to replace it with what? Aslan points to the Zealots who would go so far as to assassinate the high priest of the Temple in Jerusalem - a man who was dependent on the approval of the hated Romans for his power.
From my own gaming experience introducing these types of concepts would need to be done with a delicate hand. Not surprisingly, religion is a touchy subject, with people having a variety of beliefs. I'm a so-liberal-are-you-sure-you're-a-Catholic Catholic. An agnostic player in my gaming group was incredibly uncomfortable with the idea of this sort of game, one of the reasons I never used Testament. Were I to try such an undertaking today, I think I'd take one of two approaches. If I wanted to strongly emphasize the religious aspects I think I'd actually make my own religions and cultures, albeit ones clearly inspired by real ones in the manner that Robert E. Howard did in his Conan stories. The other way I'd go, one I think more likely, would be to use a more historic view of religions. The people might believe in the power of healing magic but that doesn't make it real beyond a placebo effect. To my mind this seems a good option to use Cthulhu Invictus and take inspiration from Richard Tierney's Simon Magus tales.