This is one of the major problems with religion. On the one hand they tell you that one cannot truly know the mind of God, and on the other hand they tell you EXACTLY how God wants you to behave. How can both be true?
Personally, I find it impossible to trust anyone who proclaims that he knows what God wants. They may believe they know, and might even believe they are actually DOING what God wants, but I still don't think they can be trusted to have MY welfare at heart. I always feel they are more interested in my checkbook than my soul.