The blade wears out the sheath.
More French Proverbs:
A goaded ass must trot.French
A mother can more easily feed seven children than seven children can feed one mother.
French
Two sparrows upon one ear of corn make ill agreement.
French
White meal is not got out of a coal-sack.
French
As the man is worth his land is worth.
French
One may go a long way after one is tired.
French