Okay, why?

A common conversation between me and Eldest these days goes like this:

Me: "Would please [do X]?"
Eldest: "Why?"
M: "No, you need to say okay."
E: "Okay, why?"
M: "No, just 'Okay'."
E: [whimpering] "Okay. Why?"

It has brought me to realize how easy it is to assume that understanding is as important as obeying. But it's not, and when God tells us to do something, we really need to just reply with, "Okay," no matter what the circumstances are. And then of course we need to obey. Maybe when we say okay and obey He'll tell us why. Maybe after a little time has passed there will be a good time to ask why, but if we really need to know why He'll tell us, and right now we're too small and upset to listen to and understand the why, so we just need to trust and obey.