"Is what is moral commanded by God because it is moral, or is it moral because it is commanded by God?"
This is known as the Euthyphro dilemma and is apparently quite a puzzler for theologians as allegedly they have never been able to crack it (possibly beating even the omnipotence paradox) ever since it was first thought up by Plato.
The basic problem is that if God commands only moral things because they're moral, then the whole morality thing is something pre-existing Creation and he's only passing it on.
It gets worse if you try to argue that whatever God says is moral, just because He says so: firstly, there's no point in considering God 'good' anymore, because whatever He says is good by definition. It means that if He had described murder and rape as virtues, then those would have been the moral choice.
Of course, you could also consider morality as emerging from an evolutionary beneficial set of traits of cooperation and cohabitation within the species, but who'd believe that?
Here he is, the clever little sod.
I hope Mr. MadnessOfArt.com doesn't mind me stealing his bandwith.
So behave, you endless torrent of visitors streaming through my blog every day. Oh, and say hi to dad for me.