There is no good in preaching to the hungry.
More German Proverbs:
The wise person has long ears and a short tongue.German
Everybody's companion is nobody's friend.
German
Pigeons are taken when crows fly at pleasure.
German
The fault of another is a good teacher.
German
Don't cry "Hurra!" till you are over the ditch.
German
Straying shepherd, straying sheep.
German