Vyāsadeva summarized all Vedic knowledge for scholars and philosophers in what is called the Vedānta-sūtra. This is the last word of the Vedas.
Originally there was only one Veda, and there was no necessity of reading it. People were so intelligent and had such sharp memories that by once hearing from the lips of the spiritual master they would understand. They would immediately grasp the whole purport. But five thousand years ago Vyāsadeva put the Vedas in writing for the people in this age, Kali-yuga. He knew that eventually the people would be short-lived, their memories would be very poor, and their intelligence would not be very sharp. "Therefore, let me teach this Vedic knowledge in writing." He divided the Vedas into four: Ṛg, Sāma, Atharva and Yajur. Then he gave the charge of these Vedas to his different disciples. He then thought of the less intelligent class of men—strī, śūdra and dvija-bandhu. He considered the woman class and śūdra class (worker class) and dvija-bandhu. Dvija-bandhu refers to those who are born in a high family but who are not properly qualified. A man who is born in the family of a brāhmaṇa but is not qualified as a brāhmaṇa is called dvija-bandhu. For these persons he compiled the Mahābhārata, called the history of India, and the eighteen Purāṇas. These are all part of the Vedic literature: the Purāṇas, the Mahābhārata, the four Vedas and the Upaniṣads. The Upaniṣads are part of the Vedas. Then Vyāsadeva summarized all Vedic knowledge for scholars and philosophers in what is called the Vedānta-sūtra. This is the last word of the Vedas.
Vyāsadeva personally wrote the Vedānta-sūtra under the instructions of Nārada, his Guru Mahārāja (spiritual master)