{literary} A person who wears fine clothes may not be as good as he looks. - A proverb. * /Mary is pretty and she wears pretty clothes, but she is very mean. Fine feathers do not make fine birds./ Compare: HANDSOME IS AS HANDSOME DOES.
FINE FEATHERS DO NOT MAKE FINE BIRDS
Meaning of FINE FEATHERS DO NOT MAKE FINE BIRDS in English
Dictionary of English idioms . Словарь английских идиом. 2012