A thief who steals from a thief is not a thief.
More German Proverbs:
Let your head be more than a funnel to your stomach.German
God helps the strongest.
German
Old age is a disease that you die from.
German
When the cat's away the mice play.
German
Follow Love and it will flee, flee love and it will follow thee.
German
Neighbour once over the hedge, neighbour over it again.
German