Bhagavatapurana 1.4.19

1.4.19

cāturhotraṃ karma śuddhaṃ prajānāṃ vīkṣya vaidikam /
vyadadhādyajñasantatyai vedam ekaṃ caturvidham //

19, 20. Perceiving that the sacrificial duty with the four priests prescribed in the *Vedas* is the way to purity for men, he divided the one Veda into four for the sake of the uninterrupted tradition of sacrifices. The divisions thus restored of the Vedas are four, Ṛig, Yajur, Sama and Atharvan; Itihasas and Puranas are said to form the fifth Veda.