As the mistake was carried out because of the god Indra, he grants Hanuman a wish that his entire body could be as robust as Indra's Vajra, and that his Vajra also can not damage him. In addition to Indra other gods have also granted him needs: the God Agni https://shanimandirsouthaustralia.blogspot.com/2024/08/the-significance-of-hanuman-jayanti.html