As The error was done by the god Indra, he grants Hanuman a desire that his physique would be as sturdy as Indra's Vajra, and that his Vajra can also not damage him. Along with Indra other gods have also granted him wishes: the God Agni granted Hanuman a want https://shanitempleadelaide.blogspot.com/2024/06/hanuman-mandir-adelaide-revered-hindu.html