Don't make use of another's mouth unless it has been leant to you.

Related:

• Experience is the comb that nature gives us when we are bald.
  Belgian...
• Money leant to a friend must be recovered from an enemy.
  German...
• No call alligator long mouth till you pass him. --
  Jamaican...
• Don't open a shop unless you know how to smile. --
  Jewish...
• Don't speak unless you can improve on the silence. -
  Spanish...
• Don't open a shop unless you know how to smile.
  Jewish...
• Don't speak unless you can improve on the silence.
  Spanish...
• Let him make use of instinct who cannot make use of reason.
  English...