Novel about alien war between "Creators and Creatures" - please help me identify

I have another sci-fi short story I cannot remember the title of.

A spaceship with two human beings is blocked by an enormous alien spaceship. Their occupants ask, "Which side of the war you are?" The humans answer that they do not know what they are talking about, and they were explained that in the Galaxy there is a huge war between Creators and Creatures, robot-like beings. The alien spaceship contains Creatures, so the human replied "we are creatures too"; the aliens then asked them to prove it. Eventually the humans sent them a copy of the Bible, which should have settled the question: the aliens agreed that the humans were creatures, but then they added "Your Creator seems to be really important. Bring us to Him. The final catchline was something like "You cannot ever find a priest, when you need it!"

Could someone help me?