Yaajnavalkya - Epic Characters of Puranas

Yaajnavalkya, son of Sage Brahmaratha and Sunanda, was a rare brahmajnani. It is said that the Lord initiated him into the Vedas even as he  was in his mother's womb. He was born with the blessings of the Sun God. He had the privilege of studying all the four Vedas from the four respective gurus- Paila, Vaishampayana, Jaimini and Sumanthu. He mastered the Karmakanda(which describes the performance of yajnas) and the Jnanakanda(which describes the Godhead).
In trying to single handedly help one of his gurus (Vaishampayana) to free him from the sin of killing a brahmin which the guru had earned, Yaajnavalkya ended up inviting the guru's wrath. The guru thought that the sage had been arrogant by suggesting that he  was capable of handling the situation alone. This was when he had to give up all the knowledge that he had earned. But, he did it with grace and left the gurukula.
The knowledge that he gave up was received by the rishis and this came to be known as Thaithariya, a branch of Yajurveda. Lord Suryadeva initiated him into newer aspects of Yajurveda that hadn't been revealed to anyone till then. This came to be known as Shukla Yajurveda. Yaajnavalkya taught this to Kanva, Madhyandina and to his other disciples. Thus his preceptor's curse turned out to be a blessing.
Yaajnavalkya got married to Kathyayini. King Janaka was on the lookout for a brahmajnani whom he could accept as his preceptor. In the conference of mighty scholars that the king had organized for the purpose, Yaajnavalkya shone as he was accepted to be the greatest of brahmajnanis. The sage accepted Maithreyi as his spiritual partner as no woman other than the wife was allowed to stay on the ashram premises.
In course of time, the sage wished to free himself of all worldly attachments and aim for salvation. The Ishavasya Upanishad, which is the smallest Upanishad, represents Yaajnavalkya's philosophy. It contains in a nutshell the ideas of knowledge, devotion and action. In other words, it teaches us the art of living and gives us supreme knowledge of Atma and Paramatma. Yaajnavalkya's greatness was acknowledged by Sri Shankaracharya and other great religious leaders.