As the mistake was performed with the god Indra, he grants Hanuman a want that his entire body will be as robust as Indra's Vajra, and that his Vajra can also not hurt him. In conjunction with Indra other gods have also granted him wishes: the God Agni granted Hanuman https://hanuman-shabhar-mantra40245.mybuzzblog.com/16871004/beej-mantra-no-further-a-mystery