It all started when a celestial nymph named Anjana was cursed by Lord Brahma to turn into a monkey. When she apologised, Lord Brahma's heart melted. Though taking back a curse was not an option, he said that she would regain her original form after giving birth to a monkey. He also added that the child would attain popularity throughout the universe.
Lord Indra, the king of gods saw Lord Hanuman approaching the sun and understood the matter. In order to stop him, he threw his weapon, the Vajra (thunderbolt). The weapon injured Hanuman who then fell down.
This infuriated his father, Lord Vayu. The lord of wind decided to go on a strike. Things went helter-skelter without the wind. Neither could the water-filled clouds move, nor could the soft breeze save people from the excessive heat of the sun. The atmosphere lost its balance in the absence of wind.
To calm down Lord Vayu, all the gods started giving blessings to Lord Hanuman. Lord Brahma said that no weapon would be able to hurt Hanuman, he would be able to change his form and travel everywhere he wanted. Lord Indra said that the Vajra would no more hurt Hanuman and that his body would become more powerful than the weapon. Lord Varun, offered him protection from water and Lord Agni from fire.
While Lord Yama blessed him with a healthy life and immortality, Lord Surya gave him the power to change his size at will. Similarly, Lord Vishwakarma, the divine architect blessed him with safety from all the objects that he created. Hence this multitude of boons made him so strong and powerful.
Lord Hanuman is often described as the most powerful, invincible and immortal God. It is said that he still exists on earth in various forms and comes as and when his devotees call him for help. You can find many devotees even today who claim about either having seen him or experienced his powers. But how did he become so powerful? Here is the answer.