SB 1.3.41

tad idaṁ grāhayām āsa
 sutam ātmavatāṁ varam
sarva-vedetihāsānāṁ
 sāraṁ sāraṁ samuddhṛtam
Word for word: 
tat — that; idam — this; grāhayām āsa — made to accept; sutam — unto his son; ātmavatām — of the self-realized; varam — most respectful; sarva — all; veda — Vedic literatures (books of knowledge); itihāsānām — of all the histories; sāram — cream; sāram — cream; samuddhṛtam — taken out.
Translation: 
Śrī Vyāsadeva delivered it to his son, who is the most respected among the self-realized, after extracting the cream of all Vedic literatures and histories of the universe.
Purport: 

Men with a poor fund of knowledge only accept the history of the world from the time of Buddha, or since 600 B.C., and prior to this period all histories mentioned in the scriptures are calculated by them to be only imaginary stories. That is not a fact. All the stories mentioned in the Purāṇas and Mahābhārata, etc., are actual histories, not only of this planet but also of millions of other planets within the universe. Sometimes the history of planets beyond this world appears to such men to be unbelievable. But they do not know that different planets are not equal in all respects and that therefore some of the historical facts derived from other planets do not correspond with the experience of this planet. Considering the different situation of different planets and also time and circumstances, there is nothing wonderful in the stories of the Purāṇas, nor are they imaginary. We should always remember the maxim that one man’s food is another man’s poison. We should not, therefore, reject the stories and histories of the Purāṇas as imaginary. The great ṛṣis like Vyāsa had no business putting some imaginary stories in their literatures.

In the Śrīmad-Bhāgavatam historical facts selected from the histories of different planets have been depicted. It is therefore accepted by all the spiritual authorities as the Mahā-purāṇa. The special significance of these histories is that they are all connected with activities of the Lord in a different time and atmosphere. Śrīla Śukadeva Gosvāmī is the topmost personality of all the self-realized souls, and he accepted this as the subject of studies from his father, Vyāsadeva. Śrīla Vyāsadeva is the great authority, and the subject matter of Śrīmad-Bhāgavatam being so important, he delivered the message first to his great son Śrīla Śukadeva Gosvāmī. It is compared to the cream of the milk. Vedic literature is like the Milk Ocean of knowledge. Cream or butter is the most palatable essence of milk, and so also is Śrīmad-Bhāgavatam, for it contains all palatable, instructive and authentic versions of different activities of the Lord and His devotees. There is no gain, however, in accepting the message of Bhāgavatam from the unbelievers, atheists and professional reciters who make a trade of Bhāgavatam for the laymen. It was delivered to Śrīla Śukadeva Gosvāmī, and he had nothing to do with the Bhāgavata business. He did not have to maintain family expenses by such trade. Śrīmad-Bhāgavatam should therefore be received from the representative of Śukadeva, who must be in the renounced order of life without family encumbrance. Milk is undoubtedly very good and nourishing, but when it is touched by the mouth of a snake it is no longer nourishing; rather, it becomes a source of death. Similarly, those who are not strictly in the Vaiṣṇava discipline should not make a business of this Bhāgavatam and become a cause of spiritual death for so many hearers. In the Bhagavad-gītā the Lord says that the purpose of all the Vedas is to know Him (Lord Kṛṣṇa), and Śrīmad-Bhāgavatam is Lord Śrī Kṛṣṇa Himself in the form of recorded knowledge. Therefore, it is the cream of all the Vedas, and it contains all historical facts of all times in relation with Śrī Kṛṣṇa. It is factually the essence of all histories.