As the mistake was done by the god Indra, he grants Hanuman a wish that his body would be as potent as Indra's Vajra, Which his Vajra may not hurt him. Coupled with Indra other gods have also granted him wishes: the God Agni granted Hanuman a wish that fire https://alphonseu630ehk0.blogozz.com/35981127/the-ultimate-guide-to-hanuman