As the error was done from the god Indra, he grants Hanuman a want that his human body might be as potent as Indra's Vajra, Which his Vajra can also not hurt him. Together with Indra other gods have also granted him wishes: the God Agni granted Hanuman a wish https://wwndirectory.com/listings874485/the-single-best-strategy-to-use-for-hanuman