From the conclusion to this theological article at Monergism.com.

Perhaps a story from the life of Martin Luther would be instructive here: when some inquisitive theologian asked him what God was doing before he created the world, Luther quipped, “He was busy creating hell for foolish theologians who pry into such questions”. The response is a little tongue-in-cheek, of course, but perhaps there is some wisdom in it, particularly when we are addressing the lapsarian question.