I'm reading Bible, and i saw a sentence:
Never forget: “A righteous man’s supplication, when it is at work, has much force.”—James 5:16.
What does "when it is at work, has much force" mean? I've searched on http://dictionary.cambridge.org/dictionary/english/be-at-work, and see that "be at work"means "to be having an effect, usually an obvious or bad effect", so "when it is at work" will mean "your prayer receive good result", right? And can you explain to me the expression "has much force"? Thank you!