Often an SS man would for a while enforce some nonsensical rule, originating in a whim of the moment. Usually it was quickly forgotten, but there were always some old prisoners who continued to observe it and tried to enforce it on others long after the SS had lost interest.
The order was never repeated, and many prisoners did not even carry it out the first time, since the SS, as was often the case, gave the order, stood around for a few minutes, and then left. Until he was gone, every prisoner busied himself with carrying out the order, after which they promptly quit. Nevertheless there were some old prisoners who not only continued to wash the insides of their shoes every day but cursed all who failed to do so as being negligent and dirty. These prisoners believed firmly that all rules set down by the SS were desirable standards of behavior, at least in the camp.
Bruno Bettelheim, "The Informed Heart. A study of the psychological consequences of living under extreme fear and terror", chapter 4 "Behavior in Extreme Situations: Coercion", section "Adjustment for Survival", subsection "Final adjustment".