Couple of mine are from Three Penny Opera:

Erst kommt das Fressen, dann kommt die Moral.

Tr. First feed the belly, then talk right from wrong.

and

Die im Dunkeln sieht man nicht.

Tr. You don't see the one in the dark.

Note regarding Fressen. In German there are two words for eating, essen is the eating as done by humans and fressen is the eating as done by animals. I take the Three Penny line to mean that one eats for survival before one worries about morality.