As the error was finished by the god Indra, he grants Hanuman a desire that his body would be as potent as Indra's Vajra, Which his Vajra can also not harm him. As well as Indra other gods have also granted him needs: the God Agni granted Hanuman a want https://medium.com/@HinduTempleAdelaide/hindu-temple-in-adelaide-a-sacred-place-for-worship-and-devotion-414718e17e6b