Bhagavatapurana 12.7.9

12.7.9

sargo 'syātha visargaś ca vṛtti-rakṣāntarāṇi ca /
vaṃśo vaṃśānucarītaṃ saṃsthā hetur apāśrayaḥ //

9. & 10. Of this Universe, the creation (of the main principles), the creation in detail, subsistence, protection, the periods of Manus, their races, the history of their descendants, destruction and the cause (motive power) and the main support—of these ten topics a Purana is composed, as the sages, who know the fact, state; some say, O Brahmin, that a Purana has five characteristics or five topics to deal with, making a distinction as great and small Puranas.