In case of words implying 'fear' and 'protection from danger' that from which the danger of fear proceeds is called apādāna kāraka,
The verbs signifying 'fear' or 'protection' govern the object feared of, or the danger to be protected from, in the ablative case. Thus चौरेभ्यो बिभेति he is afraid of thieves, चौरेभ्य उद्विजते he is agitated because of the thieves. चौरेभ्यस्त्रायते or रक्षति. He protects or saves from the thieves.
Why do we say 'the cause of fear (bhaya-hetu) is put in the ablative case'? Observe अरण्ये बिभेति or त्रायते he fears or protects in the forest.,