He (Vyasadeva) has expanded the Vedas into eighteen Puranas and has summarized Vedic knowledge in the Vedanta-sutra

Expressions researched:
"He has expanded the Vedas into eighteen Puranas and has summarized Vedic knowledge in the Vedanta-sutra"

CC Madhya-lila

Śrīla Vyāsadeva is called Mahāmuni. He is also known as Vedavyāsa because he has compiled so many śāstras. He has divided the Vedas into four divisions—Sāma, Ṛg, Yajur and Atharva. He has expanded the Vedas into eighteen Purāṇas and has summarized Vedic knowledge in the Vedānta-sūtra.

CC Madhya 20.353, Translation and Purport:

“The Vedic literatures composed by the omniscient Mahāmuni Vyāsadeva are evidence of all spiritual existence. Only through these revealed scriptures can all conditioned souls attain knowledge.

Foolish people try to concoct knowledge by manufacturing something in their brains. That is not the real way of knowledge. Knowledge is śabda-pramāṇa, evidence from the Vedic literature. Śrīla Vyāsadeva is called Mahāmuni. He is also known as Vedavyāsa because he has compiled so many śāstras. He has divided the Vedas into four divisions—Sāma, Ṛg, Yajur and Atharva. He has expanded the Vedas into eighteen Purāṇas and has summarized Vedic knowledge in the Vedānta-sūtra. He also compiled the Mahābhārata, which is accepted as the fifth Veda. The Bhagavad-gītā is contained within the Mahābhārata. Therefore the Bhagavad-gītā is also Vedic literature (smṛti). Some of the Vedic literatures are called śrutis, and some are called smṛtis. Śrīla Rūpa Gosvāmī recommends in the Bhakti-rasāmṛta-sindhu (1.2.101):

śruti-smṛti-purāṇādi-pañcarātra-vidhiṁ vinā

aikāntikī harer bhaktir utpātāyaiva kalpate

(Brs. 1.2.101)

Unless one refers to śāstra (śruti, smṛti, purāṇa and so on), one's spiritual activity simply disturbs society. There is no king or government to check people, and therefore society has fallen into a chaotic condition as far as spiritual understanding is concerned. Taking advantage of this chaotic condition, many rascals have appeared and proclaimed themselves incarnations of God. As a result, the entire population is indulging in sinful activities such as illicit sex, intoxication, gambling and meat-eating. Out of many sinful people, many so-called incarnations of God are emerging. This is a very regrettable situation, especially in India.