As the mistake was carried out from the god Indra, he grants Hanuman a would like that his overall body can be as sturdy as Indra's Vajra, and that his Vajra can also not hurt him. Coupled with Indra other gods have also granted him wishes: the God Agni granted https://reidflgan.blogzet.com/the-definitive-guide-to-hanuman-51787150