As the error was finished from the god Indra, he grants Hanuman a want that his overall body would be as robust as Indra's Vajra, Which his Vajra can also not harm him. Together with Indra other gods have also granted him needs: the God Agni granted Hanuman a want https://indiantempleadelaide.tech.blog/2024/05/17/hanuman-mandir-a-spiritual-haven-in-south-australia/