SB 12.13.3
purana-sankhya-sambhutim
asya vacya-prayojane
danam danasya mahatmyam
pathades ca nibodhata
Translation:
Now please hear a summation of the verse length of each of the Puranas. Then hear of the prime subject and purpose of this Bhagavata Purana, the proper method of giving it as a gift, the glories of such gift-giving, and finally the glories of hearing and chanting this literature.
Purport:
Srimad-Bhagavatam is the best of all Puranas. Srila Visvanatha Cakravarti Thakura explains that the other Puranas will now be mentioned just as the assistants of a king are mentioned in connection with his glorification.