So back to what Gavra_At_Work suggested ???? ?????, that it is a siman, not a ????. The very fact that g-d told you to do it is a proof, as it were, that it is a good idea, but not necessarily because He told you to do it. I don’t like that idea.
It wasn’t a Chazarah. The point is still true (IMHO) that Hashem commanding you is a siman and not a sibah, but that has nothing to do with the “why do it” question. Who says you have to do what is good?
DaasYochid – Very good point.