As The error was carried out with the god Indra, he grants Hanuman a desire that his overall body could be as strong as Indra's Vajra, Which his Vajra can also not hurt him. As well as Indra other gods have also granted him needs: the God Agni granted Hanuman https://share.evernote.com/note/9f1ba5dc-5509-8c3d-485a-6916a1dedf05