From Longman Dictionary of Contemporary Englishheaven forbidheaven forbidHOPEused to say that you very much hope something will not happen What would you do financially if, heaven forbid, your husband died? → heaven
Examples from the Corpus
heaven forbid• Heaven forbid you should have an accident!• And heaven forbid that you should be served by some one in a chain coffee house with a regional accent.• Or, heaven forbid, ridicule him? 