One scabbed sheep will mar a whole flock.
More Danish Proverbs:
Vipers breed vipers.Danish
Mischief comes soon enough.
Danish
Deceit is in haste, but honesty can wait a fair leisure.
Danish
Fish and guests stink after three days.
Danish
Every fool can find faults that a great many wise men can't remedy.
Danish
Buy in the cheapest market and sell in the dearest.
Danish