If you look at both the OT and the NT, as OnceConvinced pointed out, there are actually huge differences and alot of changes. Now,
goat wrote:They way that most Jews explain it is 'It is not God who changes, but rather our understanding of God.'
and this works for Judaism, if we leave out the NT. Even in places in the Hebrew Bible where "God changed" such things as temple sacrifice, etc., it was due more to the circumstances. The Jews were captive in Babylon, away from the temple. So the change was more of necessity. The changes between the OT and NT were blatant. Of course, I believe that it was Paul who made those changes, and not Jesus. Paul seemed to be the instigator of all the problems found in Christianity. Jesus said that anyone who teaches another to not follow the Law, "it would be better for a millstone tied around his neck, and cast into the sea", and yet Paul says that the Law is done away with. Jesus kept to the Hebrew scriptures, to the best of his ability, and Paul trashed all of that. Paul made the changes.