Birth of Atharva Veda

The four sages Sanak,Sanandan,Sanatan,Sanat were learned brahmins. They were the sons of Lord Brahma. They were very proud of their father, Brahma because he was the creator of the holy books , Vedas. They were aware of three Vedas,- Rigved,Yajurved, and Samveda and considered that the whole knowledge is complete in three books.On the other hand Sage Atharva approached Lord Shiva to get approval of his knowledge which he gathered from the universe using his divine powers. Lord Shiva, impressed by his creation and blessed Sage Atharva that his book of knowledge would constitute the list of Vedas and will be called as ‘Atharvaveda’. When this news reached the sons of Lord Brahma, they protested as according to them the other three Vedas was a complete set of knowledge and there was no need of fourth Veda. They argued Lord Shiva and challenged his authority to certify fourth veda.  . Finally it was decided that whether to certify fourth Veda or not depends upon the result of debate. Goddess Saraswati was appointed as judge. The four Sages fired too much and too complicated questions to Lord Shiva and there were very confident of their victory as they underestimated Lord Shiva. But Shiva, who is the Lord of all the supreme knowledge, answered each and every question . The Sages accept their defeat gracefully and asked for forgiveness. Since then Artharva Ved was added to the list of Vedas , making the total four.  The Sages went to their brother Prajapati Daksha who was bitter rival of Lord Shiva. On listening about the defeat of his four brothers, he cursed them to be small child. After that the four sages turned into small children. Since the sages were very learned , so they thanked their brother for the curse because after becoming kids their urge for learning more would be greater.