One day Parvati posted Ganesha on guard duty at the door. Parvati ordered Ganesha not to allow anyone to enter the house. After a while, Shiva came home. Even after telling him that he is the husband of Parvati, Ganesha didn't allow him to enter inside. Shiva got angry and cut off the head of Ganesha and threw it away using his trident.
When Parvati knew this, she became furious and decided to destroy the entire Creation. Lord Brahma, being the creator, pleaded that she reconsiders her plan. She agreed but with two conditions one, that Ganesha be brought back to life and two, that he be forever worshiped before all the other gods.
Lord Shiva sent Brahma to bring the head of the first creature
he crosses with its head facing north. Brahma soon returned with the head of a
strong and powerful elephant, which Shiva fixed onto Ganesha's body. Breathing
new life into him, Shiva declared Ganesha to be his elder son and made him
chief of his army and Shiva gave him the status of being foremost among the
gods.
