From Longman Dictionary of Contemporary Englishheaven help somebodyheaven help somebodya) DANGEROUSused to express sympathy for someone who is in a dangerous or difficult situation ‘The two boys are going to the dentist on Thursday.’ ‘Heaven help the dentist.’ b) ANGRYused to say that you will be very angry with someone if they do something Heaven help him if he ever comes back here again! → heaven
Examples from the Corpus
heaven help somebody• Heaven help us if it snows again. 